app-misc/regex-markup: fix modern C issue in configure

Closes: https://bugs.gentoo.org/923618
Signed-off-by: Sam James <sam@gentoo.org>

app-misc/regex-markup/files/regex-markup-0.10.0-c99.patch

@@ -0,0 +1,11 @@
+https://bugs.gentoo.org/923618
+--- a/m4/regex.m4
++++ b/m4/regex.m4
+@@ -34,6 +34,7 @@ AC_DEFUN([gl_INCLUDED_REGEX],
+ 		   jm_cv_func_working_re_compile_pattern,
+       AC_TRY_RUN(
+ [#include <stdio.h>
++#include <stdlib.h>
+ #include <string.h>
+ #include <regex.h>
+ 	  int

app-misc/regex-markup/regex-markup-0.10.0-r3.ebuild

@@ -1,4 +1,4 @@
-# Copyright 1999-2023 Gentoo Authors
+# Copyright 1999-2024 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=8
@@ -17,6 +17,7 @@ IUSE="examples nls"
 PATCHES=(
 	"${FILESDIR}"/${P}-locale.patch
 	"${FILESDIR}"/${PN}-0.10.0-r2-configure.patch
+	"${FILESDIR}"/${PN}-0.10.0-c99.patch
 )
 
 src_prepare() {