(HASHBITS): Removed.

(HASH, struct set, canon_hash, safe_hash, remove_from_table):
Generate and use unsigned hash values, to avoid potential trouble
with signed shift/overflow.
Also name variables consistently: "hash", not "hash_code".
(lookup, lookup_for_remove, insert, merge_equiv_classes): Likewise.
(invalidate, rehash_using_reg, invalidate_for_call): Likewise.
(find_best_addr, record_jump_cond, cse_insn):  Likewise.

From-SVN: r6431