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.
to be not quite right, and all sets of rules need to be updated
to match the latest DRC rule parsing. Also, plowing does not
handle contact types correctly.
enabling the "plow" command. At this time, however, not all
rules are being implemented correctly given the numerous changes
to the DRC handling since the last time "plow" was working. Fixes
are ongoing.