Changes to HACKING

[Dirk Herrmann]

Hello everybody.

The updated text in HACKING still talks of warnings about variables being
clobbered by longjmp/vfork in eval.c.  However, these warnings are no
longer issued when compiling eval.c, but rather when compiling
continuations.c.

Moreover, this warning can be fixed by simply declaring the variable cont
in scm_make_continuation as volatile.  As this code is no longer part of
the evaluator, it shouldn't be a big performance hit any more.  Therefore,
we could get rid of that section in HACKING completely.

Best regards,
Dirk Herrmann