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/vfs/device.c

@@ -146,7 +146,7 @@ PUBLIC void dev_status(message *m)
 		break;
 
 	if (d >= NR_DEVICES) return;
-	if (dmap[d].dmap_async_driver) {
+	if (dmap[d].dmap_style == STYLE_DEVA) {
 		printf("dev_status: not doing dev_status for async driver %d\n",
 			m->m_source);
 		return;
@@ -416,7 +416,7 @@ int suspend_reopen;		/* Just suspend the process */
 	/* fp is uninitialized at init time. */
 	if(!fp) panic("SUSPEND on NULL fp");
 
-	if ((flags & O_NONBLOCK) && !dp->dmap_async_driver) {
+	if ((flags & O_NONBLOCK) && !(dp->dmap_style == STYLE_DEVA)) {
 		/* Not supposed to block. */
 		dev_mess.m_type = CANCEL;
 		dev_mess.IO_ENDPT = ioproc;