Fix recursion stack estimator

Due to inlining match() by recent GCC, the stack estimator reported 4-bytes
stack consumption.

Author: Sergei Golubchik <vuvova@gmail.com>
<https://bugs.exim.org/show_bug.cgi?id=2173>

diff --git a/pcre/pcre_exec.c b/pcre/pcre_exec.c
--- a/pcre_exec.c
+++ b/pcre_exec.c
@@ -509,6 +509,12 @@
                  (e.g. stopped by repeated call or recursion limit)
 */
 
+#ifdef __GNUC__
+static int
+match(REGISTER PCRE_PUCHAR eptr, REGISTER const pcre_uchar *ecode,
+  PCRE_PUCHAR mstart, int offset_top, match_data *md, eptrblock *eptrb,
+  unsigned int rdepth) __attribute__((noinline,noclone));
+#endif
 static int
 match(REGISTER PCRE_PUCHAR eptr, REGISTER const pcre_uchar *ecode,
   PCRE_PUCHAR mstart, int offset_top, match_data *md, eptrblock *eptrb,
