Driver mapping refactory.

VFS CHANGES:
- dmap table no longer statically initialized in VFS
- Dropped FSSIGNON svrctl call no longer used by INET

INET CHANGES:
- INET announces its presence to VFS just like any other driver

RS CHANGES:
- The boot image dev table contains all the data to initialize VFS' dmap table
- RS interface supports asynchronous up and update operations now
- RS interface extended to support driver style and flags

servers/inet/Makefile

@@ -12,8 +12,8 @@ SRCS=	buf.c clock.c inet.c inet_config.c \
 
 .PATH:	${.CURDIR}/generic
 
-DPADD+=	${LIBSYS}
-LDADD+=	-lsys
+DPADD+=	${LIBDRIVER} ${LIBSYS}
+LDADD+=	-ldriver -lsys
 
 MAN=