[Darwin, committed] Add include guard to darwin-protos.h

[Iain Sandoe]

The Darwin protos header is missing an include guard, this adds one.

tested on x86_64-darwin16
applied to mainline
thanks
Iain

gcc/ChangeLog:

2019-11-08  Iain Sandoe  <i...@sandoe.co.uk>

        * config/darwin-protos.h: Add include quard.

diff --git a/gcc/config/darwin-protos.h b/gcc/config/darwin-protos.h
index afeca81..e6721c7 100644
--- a/gcc/config/darwin-protos.h
+++ b/gcc/config/darwin-protos.h
@@ -17,6 +17,9 @@ You should have received a copy of the GNU General Public 
License
 along with GCC; see the file COPYING3.  If not see
 <http://www.gnu.org/licenses/>.  */
 
+#ifndef CONFIG_DARWIN_PROTOS_H
+#define CONFIG_DARWIN_PROTOS_H
+
 extern void darwin_init_sections (void);
 extern int name_needs_quotes (const char *);
 
@@ -123,3 +126,5 @@ extern void darwin_override_options (void);
 extern void darwin_patch_builtins (void);
 extern void darwin_rename_builtins (void);
 extern bool darwin_libc_has_function (enum function_class fn_class);
+
+#endif /* CONFIG_DARWIN_PROTOS_H */