* 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.