[perl #130522] don't try to find_by_class outside the string

If the calculated latest start position to try is before our current
start position, stop immediately: else we can read out of bounds,
and end up doing unnecessary work.

regexec.c

@@ -1974,10 +1974,8 @@ S_find_byclass(pTHX_ regexp * prog, const regnode *c, char *s,
          * trying that it will fail; so don't start a match past the
          * required minimum number from the far end */
         e = HOP3c(strend, -((SSize_t)ln), s);
-
-        if (reginfo->intuit && e < s) {
-            e = s;			/* Due to minlen logic of intuit() */
-        }
+        if (e < s)
+            break;
 
         c1 = *pat_string;
         c2 = fold_array[c1];
@@ -2021,10 +2019,6 @@ S_find_byclass(pTHX_ regexp * prog, const regnode *c, char *s,
          */
         e = HOP3c(strend, -((SSize_t)lnc), s);
 
-        if (reginfo->intuit && e < s) {
-            e = s;			/* Due to minlen logic of intuit() */
-        }
-
         /* XXX Note that we could recalculate e to stop the loop earlier,
          * as the worst case expansion above will rarely be met, and as we
          * go along we would usually find that e moves further to the left.