configure: Add _FORTIFY_SOURCE=2

Add -D_FORTIFY_SOURCE=2 into CPPFLAGS if:

o it's not allready set in system headers
o optimalization is enabled

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
diff --git a/m4/ltp-fortify_source.m4 b/m4/ltp-fortify_source.m4
new file mode 100644
index 0000000..ffb22b4
--- /dev/null
+++ b/m4/ltp-fortify_source.m4
@@ -0,0 +1,39 @@
+dnl
+dnl Copyright (c) 2013 Cyril Hrubis <chrubis@suse.cz>
+dnl
+dnl This program is free software;  you can redistribute it and/or modify
+dnl it under the terms of the GNU General Public License as published by
+dnl the Free Software Foundation; either version 2 of the License, or
+dnl (at your option) any later version.
+dnl
+dnl This program is distributed in the hope that it will be useful,
+dnl but WITHOUT ANY WARRANTY;  without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+dnl the GNU General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU General Public License
+dnl along with this program;  if not, write to the Free Software
+dnl Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+dnl
+
+dnl
+dnl LTP_CHECK_FORTIFY_SOURCE
+dnl ------------------------
+dnl
+AC_DEFUN([LTP_CHECK_FORTIFY_SOURCE],[dnl
+	AC_MSG_CHECKING(whether to define _FORTIFY_SOURCE=2)
+	AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+#include <stdio.h>
+
+int main(void)
+{
+#if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__
+	return 0;
+#else
+# error Compiling without optimalizations
+#endif
+}
+])],[CPPFLAGS="$CPPFLAGS -D_FORTIFY_SOURCE=2"
+AC_MSG_RESULT(yes)],
+[AC_MSG_RESULT(no)])
+])