pkgbase: Put libbsdxml in FreeBSD-runtime

libbsdxml is used by a lot of programs so just put it in FreeBSD-runtime.

Differential Revision: https://reviews.freebsd.org/D31800
Reviewed by: emaste

lib/libexpat/Makefile

@@ -1,6 +1,6 @@
 # $FreeBSD$
 
-PACKAGE=lib${LIB}
+PACKAGE=	runtime
 EXPAT=		${SRCTOP}/contrib/expat
 
 LIB=		bsdxml