Restore digit check in mb_decode_numericentity()

I replaced it with a multiplication overflow check in
18599f9. However, we need both,
because the code for restoring the number can't handle numbers
with many leading zeros right now and I don't feel like teaching it.

Author: nikic

ext/mbstring/libmbfl/mbfl/mbfilter.c

@@ -2554,7 +2554,7 @@ collector_decode_htmlnumericentity(int c, void *data)
 		f = 0;
 		if (c >= 0x30 && c <= 0x39) {	/* '0' - '9' */
 			s = pc->cache;
-			if (s > INT_MAX/10) {
+			if (pc->digit > 9 || s > INT_MAX/10) {
 				pc->status = 0;
 				f = 1;
 			} else {

ext/mbstring/tests/mb_decode_numericentity.phpt

@@ -19,6 +19,7 @@ echo mb_decode_numericentity('&#1000000000', $convmap), "\n";
 echo mb_decode_numericentity('&#9000000000', $convmap), "\n";
 echo mb_decode_numericentity('&#10000000000', $convmap), "\n";
 echo mb_decode_numericentity('&#100000000000', $convmap), "\n";
+echo mb_decode_numericentity('&#000000000000', $convmap), "\n";
 
 ?>
 --EXPECT--
@@ -29,3 +30,4 @@ aŒbœcŠdše€fg
 &#9000000000
 &#10000000000
 &#100000000000
+&#000000000000