- Replace the for loop temporaries by locals. They cause conflicts with
the stack when being popped, while locals are properly handled in the
scope.
- Change the interface for the codegen so the for loop list doesn't live
through the whole block if it's a temporary.
- Keep track of the actual amount of local variables in the stack. Using
the size of the map is misleading in cases where multiple locals have
the same name (which is allowed when there's no shadowing).
- Added a few debug checks for temporaries, to avoid them being wrongly
manipulated in the future. They should not live more than a line of
code.
- Rearrange some of compiler code to make sure the temporaries don't
live across blocks.
