cstage rejects a binop whose two integer operands have different
types (e.g. int vs i32 from len()); wwstage accepted it, miscompiling
under no-implicit-promotion. Align wwstage UP: unifyarith now chases
aliases and loud-rejects an integer-type mismatch, routing the
ordered-comparison ops through the same path with the error message
threaded on `e`. Per the user's no-implicit-promotion decision.
Scope carve-outs: EQ/NEQ stay out of the reject (#34, the comparison
operators keep their own widening rule) and a rune literal is exempt
(#35, N_RUNELIT is still untyped at this point). Adds the 29-case
test/wcc/949_intbinop_mismatch.c and its Makefile wiring.
Hojun-Cho
9fcb3be541