Fix yield's 'input precedence' (352269, r=mrbkap).

js/src/jsopcode.c

@@ -1790,6 +1790,7 @@ Decompile(SprintStack *ss, jsbytecode *pc, intN nb)
 
 #if JS_HAS_GENERATORS
               case JSOP_YIELD:
+                op = JSOP_SETNAME;      /* turn off most parens */
                 rval = POP_STR();
                 todo = (*rval != '\0')
                        ? Sprint(&ss->sprinter,