Simplify hashfn/cmpfn calling convention

Simplify hashfn/cmpfn calling convention

* src/fns.c (cmpfn_eql, cmpfn_equal, cmpfn_user_defined)
(hashfn_eq, hashfn_equal, hashfn_eql, hashfn_user_defined):
* src/profiler.c (cmpfn_profiler, hashfn_profiler):
Use new calling convention where the return value is a fixnum
instead of EMACS_UINT.  While we’re at it, put the hash table
at the end, since that’s a bit simpler and generates better
code (at least on the x86-64).  All callers changed.
* src/fns.c (hash_lookup): Store fixnum rather than EMACS_UINT.
All callers changed.
(hash_put): Take a fixnum rather than an EMACS_UINT.
All callers changed.  Remove unnecessary eassert (XUFIXNUM does it).
* src/lisp.h (struct hash_table_test):
Adjust signatures of cmpfn and hashfn.