Legacy compiler support macro provided by TCL from a time when 'const'
did not exist.
This looks like it was put in place around the time of TCL 8.4
(from 2002 until 2013) which introduced APIs with 'const' types,
that were previously non-const. Probably due to legacy compiler
support across target platforms at the time.
Since the minimum TCL level is hardwired to 8.5 (from 2007 until
2016) it does not seem like that compatiblity is a current
requirement.
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.
Darryl L. Miles
Alessandro De Laurenzis
Tim Edwards