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

lib/libc/other/_mapdriver.c

@@ -4,18 +4,18 @@
 #include <unistd.h>
 
 
-PUBLIC int mapdriver(label, major, dev_style, force)
+PUBLIC int mapdriver(label, major, dev_style, flags)
 char *label;
 int major;
 int dev_style;
-int force;
+int flags;
 {
   message m;
   m.m2_p1 = label;
   m.m2_l1 = strlen(label);
   m.m2_i1 = major;
   m.m2_i2 = dev_style;
-  m.m2_i3 = force;
+  m.m2_i3 = flags;
   if (_syscall(FS, MAPDRIVER, &m) < 0) return(-1);
   return(0);
 }