this introduces 4 new warning disable flags:
CC_WNO_MISSING_TEMPLATE_KEYWORD
CC_WNO_REGISTER
CC_WNO_STRINGOP_OVERREAD
CC_WNO_ARRAY_BOUNDS
and documents them in README.warnings. of these, the string op
and array bounds are both problematic (real bugs) and also spurious
(not real bugs), and the other 2 are mostly temporary for older
3rd party code.
add some new uses of CC_WNO_STRINGOP_OVERFLOW.
fix m68k build for gallium and GCC 12.
832d47522a