-Werror,-Wheader-guard (Clang trunk towards 3.4)

...in external nss header; an alternative could be to use -isystem instead of -I
in gb_LinkTarget__use_nss3.

Change-Id: I399e6990dd0110e0e16baea0d20a16050acfdeb1

nss/UnpackedTarball_nss.mk

@@ -20,6 +20,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,nss,\
 	$(if $(filter WNTGCC,$(OS)$(COM)),nss/nspr-4.9-build.patch.3 \
 	nss/nss-3.13.3-build.patch.3 \
 	nss/nss.mingw.patch.3) \
+	nss/nss.wheader-guard.patch.0 \
 ))
 
 # vim: set noet sw=4 ts=4:

nss/nss.wheader-guard.patch.0

+--- mozilla/security/nss/lib/pk11wrap/secmod.h
++++ mozilla/security/nss/lib/pk11wrap/secmod.h
+@@ -34,7 +34,7 @@
+  *
+  * ***** END LICENSE BLOCK ***** */
+ #ifndef _SECMOD_H_
+-#define _SEDMOD_H_
++#define _SECMOD_H_
+ #include "seccomon.h"
+ #include "secmodt.h"
+ #include "prinrval.h"