This commit related to the dynamic creation of data that is used
to parse commands and options via Lookup.
windows/windows.h: Lookup() constify call-site
tcltk/tclmagic.c: Lookup() constify call-site
graphics/W3Dmain.c: Lookup() constify call-site
windows/windSend.c: Lookup() constify call-site
windows/windMain.c: Lookup() constify call-site
windows/windInt.h: Lookup() constify call-site
textio/txMain.c: Lookup() constify call-site
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.