Make range literal peephole optimization target "newrange"

It looks for "checkmatch", when it could be applied to anything that has
"newrange".

Making the optimization target more ranges might only be fair play when
all ranges are frozen. So I'm putting a reference to the ticket that
froze all ranges.

[Feature #15504]

compile.c

@@ -3027,13 +3027,12 @@ iseq_peephole_optimize(rb_iseq_t *iseq, LINK_ELEMENT *list, const int do_tailcal
      *
      * putobject "beg".."end"
      */
-    if (IS_INSN_ID(iobj, checkmatch)) {
-        INSN *range = (INSN *)get_prev_insn(iobj);
+    if (IS_INSN_ID(iobj, newrange)) {
+        INSN *const range = iobj;
         INSN *beg, *end;
         VALUE str_beg, str_end;
 
-	if (range && IS_INSN_ID(range, newrange) &&
-                (end = (INSN *)get_prev_insn(range)) != 0 &&
+        if ((end = (INSN *)get_prev_insn(range)) != 0 &&
                 is_frozen_putstring(end, &str_end) &&
                 (beg = (INSN *)get_prev_insn(end)) != 0 &&
                 is_frozen_putstring(beg, &str_beg)) {