* eval.c (SCM_CEVAL): Cleaned up the handling of #@dispatch.

* eval.c (SCM_CEVAL): Cleaned up the handling of #@dispatch.
Added lots of comments regarding the implementation of #@dispatch.
Changed intra-procedure communication to use t.arg1 instead of
arg2.  Removed some uses of t.arg1, t.lloc and proc as temporary
variables.  Introduced temporary variables with hopefully
descriptive names for clarification.  Replaced SCM_N?IMP by a more
explicit predicate in some places.  Use SCM_INSTANCE_HASH instead
of computing the expression explicitly.  Eliminate now unused
label nontoplevel_cdrxbegin.

* goops.h (SCM_INSTANCE_HASH): New macro.

* objects.h (SCM_CMETHOD_FORMALS, SCM_CMETHOD_BODY): New macros.