Minor hashing refactoring.

Minor hashing refactoring.

* fns.c (SXHASH_REDUCE): Move to lisp.h.
(sxhash_float): Return EMACS_UINT, for consistency with the other
hash functions.
* lisp.h (INTMASK): Now a macro, since SXHASH_REDUCE is now a
non-static inline function and therefore can't use static vars.
(SXHASH_REDUCE): Move here from fns.c, and make it inline.
* profiler.c (hashfn_profiler): Use SXHASH_REDUCE, to be consistent
with the other hash functions.