switch off 'warning treated as error' in external/nss in Win32

This prevents errors from ms sdk sal_supp.h: warning '__useHeader': macro redefinition

Change-Id: I122bbf6171c73d77970a549353dca67dd26d0300
Reviewed-on: https://gerrit.libreoffice.org/24055Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Oliver Specht <oliver.specht@cib.de>

external/nss/UnpackedTarball_nss.mk

@@ -18,6 +18,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,nss,\
 	external/nss/nss_macosx.patch \
 	external/nss/nss-win32-make.patch.1 \
 	$(if $(filter WNTMSC,$(OS)$(COM)),external/nss/nss.windows.patch \
+        external/nss/nss.nowerror.patch \
 		external/nss/nss.vs2015.patch) \
 	$(if $(filter WNTGCC,$(OS)$(COM)),external/nss/nspr-4.9-build.patch.3 \
 		external/nss/nss-3.13.3-build.patch.3 \

external/nss/nss.nowerror.patch

+diff -ur nss.org/nss/coreconf/WIN32.mk nss/nss/coreconf/WIN32.mk
+--- a/nss.org/nss/coreconf/WIN32.mk	2016-04-13 11:33:09.322294523 +0200
++++ b/nss/nss/coreconf/WIN32.mk	2016-04-13 11:33:27.744323969 +0200
+@@ -126,9 +126,9 @@
+     OS_CFLAGS += -W3 -nologo -D_CRT_SECURE_NO_WARNINGS \
+ 		 -D_CRT_NONSTDC_NO_WARNINGS
+     OS_DLLFLAGS += -nologo -DLL -SUBSYSTEM:WINDOWS
+     ifndef NSS_ENABLE_WERROR
+-        NSS_ENABLE_WERROR = 1
++        NSS_ENABLE_WERROR = 0
+     endif
+     ifeq ($(NSS_ENABLE_WERROR),1)
+         OS_CFLAGS += -WX
+     endif