re: port-macppc/54827: alloca() is broken in gcc 8 on powerpc

[matthew green <mrg%eterna.com.au@localhost>]

looking at the diff in external/gpl3/gcc/dist/gcc/config/rs6000,
i see that we have a lot changes vs eg, vs gcc-8-3-0 import or
the pkgsrc gcc 8 (which has zero rs6000/powerpc changes).

they're for ppc64, but also several other ones.

we also have patched config.gcc heavily for rs6000 and maybe
more.

things i would start with:
- revert rs6000.c changes
- revert config.gcc powerpc changes, and perhaps also the bit
  about default_gnu_indirect_function.
- try to figure out how to revert type-definitions changes

but nothing looks obvious to me.


.mrg.