Patch from Chris Emerson for PPC.  cothreads stuff was causing segfaults, because the stack needs to be initialised w...

Original commit message from CVS:
Patch from Chris Emerson for PPC.  cothreads stuff was causing segfaults,
because the stack needs to be initialised with a particular structure on
PPC, unlike x86 where it simply has items pushed or popped.
Added Chris to AUTHORS, for his trouble.