Change regerror() declaration from K&R style to ANSI C (C89)

The MSVC headers typedef errcode as int, and thus confused the compiler in
the K&R style definition. ANSI style deconfuses it.
Signed-off-by: NFrank Li <lznuaa@gmail.com>
Signed-off-by: NMarius Storm-Olsen <mstormo@gmail.com>
Acked-by: NJohannes Sixt <j6t@kdbg.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

compat/regex/regex.c

@@ -4852,11 +4852,8 @@ regexec (preg, string, nmatch, pmatch, eflags)
    from either regcomp or regexec.   We don't use PREG here.  */
 
 size_t
-regerror (errcode, preg, errbuf, errbuf_size)
-    int errcode;
-    const regex_t *preg;
-    char *errbuf;
-    size_t errbuf_size;
+regerror(int errcode, const regex_t *preg,
+	 char *errbuf, size_t errbuf_size)
 {
   const char *msg;
   size_t msg_size;