commit 86b5d591d from 20241004 by me, modified return type of
GrTextSize API in the graphics from 'void' to 'int' to convey
and error scenario to indicate when 'r' was not filled in for
the caller, but this is a multi graphics driver API interface
so requires all downstream graphics engines to also support
the return type change.
This API can error and indicates when 'Rect *r' was
successfully updated.
This commit makes the code (mostly) C99-compatible, enabling to compile
it without the -Wno-error=implicit-function-declaration flag. This
way, Magic becomes usable on arm64 architectures, specifically on Apple
computers with M1/M2 SoC.