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.
commands on selections in a cell that is not editable. Moves
and Copies were already handled correctly; this correction fixes
Delete and transforms (e.g., rotates and flips).