Document the expected normal map coordinate system where relevant

(cherry picked from commit d8808fba85)

doc/classes/CPUParticles2D.xml

@@ -240,6 +240,7 @@
 		</member>
 		<member name="normalmap" type="Texture" setter="set_normalmap" getter="get_normalmap">
 			Normal map to be used for the [member texture] property.
+			[b]Note:[/b] Godot expects the normal map to use X+, Y-, and Z+ coordinates. See [url=http://wiki.polycount.com/wiki/Normal_Map_Technical_Details#Common_Swizzle_Coordinates]this page[/url] for a comparison of normal map coordinates expected by popular engines.
 		</member>
 		<member name="one_shot" type="bool" setter="set_one_shot" getter="get_one_shot" default="false">
 			If [code]true[/code], only one emission cycle occurs. If set [code]true[/code] during a cycle, emission will stop at the cycle's end.

doc/classes/MeshInstance2D.xml

@@ -17,6 +17,7 @@
 		</member>
 		<member name="normal_map" type="Texture" setter="set_normal_map" getter="get_normal_map">
 			The normal map that will be used if using the default [CanvasItemMaterial].
+			[b]Note:[/b] Godot expects the normal map to use X+, Y-, and Z+ coordinates. See [url=http://wiki.polycount.com/wiki/Normal_Map_Technical_Details#Common_Swizzle_Coordinates]this page[/url] for a comparison of normal map coordinates expected by popular engines.
 		</member>
 		<member name="texture" type="Texture" setter="set_texture" getter="get_texture">
 			The [Texture] that will be used if using the default [CanvasItemMaterial]. Can be accessed as [code]TEXTURE[/code] in CanvasItem shader.

doc/classes/MultiMeshInstance2D.xml

@@ -17,6 +17,7 @@
 		</member>
 		<member name="normal_map" type="Texture" setter="set_normal_map" getter="get_normal_map">
 			The normal map that will be used if using the default [CanvasItemMaterial].
+			[b]Note:[/b] Godot expects the normal map to use X+, Y-, and Z+ coordinates. See [url=http://wiki.polycount.com/wiki/Normal_Map_Technical_Details#Common_Swizzle_Coordinates]this page[/url] for a comparison of normal map coordinates expected by popular engines.
 		</member>
 		<member name="texture" type="Texture" setter="set_texture" getter="get_texture">
 			The [Texture] that will be used if using the default [CanvasItemMaterial]. Can be accessed as [code]TEXTURE[/code] in CanvasItem shader.

doc/classes/Particles2D.xml

@@ -53,6 +53,7 @@
 		</member>
 		<member name="normal_map" type="Texture" setter="set_normal_map" getter="get_normal_map">
 			Normal map to be used for the [member texture] property.
+			[b]Note:[/b] Godot expects the normal map to use X+, Y-, and Z+ coordinates. See [url=http://wiki.polycount.com/wiki/Normal_Map_Technical_Details#Common_Swizzle_Coordinates]this page[/url] for a comparison of normal map coordinates expected by popular engines.
 		</member>
 		<member name="one_shot" type="bool" setter="set_one_shot" getter="get_one_shot" default="false">
 			If [code]true[/code], only one emission cycle occurs. If set [code]true[/code] during a cycle, emission will stop at the cycle's end.

doc/classes/SpatialMaterial.xml

@@ -152,6 +152,7 @@
 		</member>
 		<member name="detail_normal" type="Texture" setter="set_texture" getter="get_texture">
 			Texture that specifies the per-pixel normal of the detail overlay.
+			[b]Note:[/b] Godot expects the normal map to use X+, Y-, and Z+ coordinates. See [url=http://wiki.polycount.com/wiki/Normal_Map_Technical_Details#Common_Swizzle_Coordinates]this page[/url] for a comparison of normal map coordinates expected by popular engines.
 		</member>
 		<member name="detail_uv_layer" type="int" setter="set_detail_uv" getter="get_detail_uv" enum="SpatialMaterial.DetailUV">
 			Specifies whether to use [code]UV[/code] or [code]UV2[/code] for the detail layer. See [enum DetailUV] for options.
@@ -241,6 +242,7 @@
 		</member>
 		<member name="normal_texture" type="Texture" setter="set_texture" getter="get_texture">
 			Texture used to specify the normal at a given pixel. The [code]normal_texture[/code] only uses the red and green channels. The normal read from [code]normal_texture[/code] is oriented around the surface normal provided by the [Mesh].
+			[b]Note:[/b] Godot expects the normal map to use X+, Y-, and Z+ coordinates. See [url=http://wiki.polycount.com/wiki/Normal_Map_Technical_Details#Common_Swizzle_Coordinates]this page[/url] for a comparison of normal map coordinates expected by popular engines.
 		</member>
 		<member name="params_alpha_scissor_threshold" type="float" setter="set_alpha_scissor_threshold" getter="get_alpha_scissor_threshold">
 			Threshold at which the alpha scissor will discard values.

doc/classes/Sprite.xml

@@ -54,6 +54,7 @@
 		</member>
 		<member name="normal_map" type="Texture" setter="set_normal_map" getter="get_normal_map">
 			The normal map gives depth to the Sprite.
+			[b]Note:[/b] Godot expects the normal map to use X+, Y-, and Z+ coordinates. See [url=http://wiki.polycount.com/wiki/Normal_Map_Technical_Details#Common_Swizzle_Coordinates]this page[/url] for a comparison of normal map coordinates expected by popular engines.
 		</member>
 		<member name="offset" type="Vector2" setter="set_offset" getter="get_offset" default="Vector2( 0, 0 )">
 			The texture's drawing offset.

doc/classes/StyleBoxTexture.xml

@@ -121,6 +121,7 @@
 		</member>
 		<member name="normal_map" type="Texture" setter="set_normal_map" getter="get_normal_map">
 			The normal map to use when drawing this style box.
+			[b]Note:[/b] Godot expects the normal map to use X+, Y-, and Z+ coordinates. See [url=http://wiki.polycount.com/wiki/Normal_Map_Technical_Details#Common_Swizzle_Coordinates]this page[/url] for a comparison of normal map coordinates expected by popular engines.
 		</member>
 		<member name="region_rect" type="Rect2" setter="set_region_rect" getter="get_region_rect" default="Rect2( 0, 0, 0, 0 )">
 			Species a sub-region of the texture to use.

doc/classes/TileSet.xml

@@ -590,6 +590,7 @@
 			</argument>
 			<description>
 				Sets the tile's normal map texture.
+				[b]Note:[/b] Godot expects the normal map to use X+, Y-, and Z+ coordinates. See [url=http://wiki.polycount.com/wiki/Normal_Map_Technical_Details#Common_Swizzle_Coordinates]this page[/url] for a comparison of normal map coordinates expected by popular engines.
 			</description>
 		</method>
 		<method name="tile_set_occluder_offset">