Using `misc/scripts/fix_headers.py` on all Godot files.
Some missing header guards were added, and the header inclusion order
was fixed in the Bullet module.
That "revision" was inherited from SVN days but had been since then
used to give information about the build: "custom_build", "official",
"<some distro's build>".
It can now be overridden with the BUILD_NAME environment variable.
Removes the need for _MKSTR all over the place which has the drawback of
converting _MKSTR(UNKNOWN_DEFINE) to "UKNOWN_DEFINE" instead of throwing
a compilation error.
Fixes a bug where the VERSION_PATCH define is not yet in scope if
typedefs.h is included before version.h at compilation time.
(cherry picked from commit 3b687c5474)
