garbage collector

[Ross Paterson]

Someone here was building Hugs on powerpc-apple-darwin6.6, and getting
INTERNAL ERROR: importEntity.  The import entity in question had been
garbage collected.  Recompiling module.c without optimization avoids the
problem, so my guess is that the optimizer's use of registers is confusing
the garbage collector.  I'm starting to think that marking the C stack
isn't working very well, and wondering if this is why optimization is
turned off for some of the other files.