Apply a temporary band-aid for building devd with clang 3.4, libstdc++

and -Wsystem-headers enabled (which is the default for any non-zero
WARNS level, crazily enough!).  This is primarily meant to be MFC'd as
soon as possible.

MFC after:	3 days

sbin/devd/Makefile

@@ -13,6 +13,7 @@ LDADD=	-ll -lutil
 
 YFLAGS+=-v
 CFLAGS+=-I. -I${.CURDIR}
+CFLAGS.clang+=-Wno-keyword-compat
 
 CLEANFILES= y.output