For sys/dev/drm2/radeon, only use -fms-extensions with gcc. This flag

is only to stop gcc complaining about anonymous unions, which clang does
not do.  For clang 3.4 however, -fms-extensions enables the Microsoft
__wchar_t type, which clashes with our own types.h.

MFC after:	3 days

sys/modules/drm2/radeonkms/Makefile

@@ -1,5 +1,7 @@
 # $FreeBSD$
 
+.include <bsd.own.mk>
+
 .PATH:	${.CURDIR}/../../../dev/drm2/radeon
 
 KMOD	= radeonkms
@@ -103,7 +105,9 @@ SRCS	+=								\
 	iicbus_if.h							\
 	pci_if.h
 
-CFLAGS  += -I${.CURDIR}/../../../dev/drm2/radeon			\
-	   -fms-extensions
+CFLAGS  += -I${.CURDIR}/../../../dev/drm2/radeon
+.if ${COMPILER_TYPE} == "gcc"
+CFLAGS	+= -fms-extensions
+.endif
 
 .include <bsd.kmod.mk>