Mount updates:

- allow mounting with "none" block device
- allow unmounting by mountpoint
- make VFS aware of file system process labels
- allow m3_ca1 to use the full available message size
- use *printf in u/mount(1), as mount(2) uses it already
- fix reference leaks for some mount error cases in VFS

include/sys/mount.h

@@ -7,6 +7,7 @@
 
 #define MS_RDONLY	0x001	/* Mount device read only */
 #define MS_REUSE	0x002	/* Tell RS to try reusing binary from memory */
+#define MS_LABEL16	0x004	/* Mount message points to 16-byte label */
 
 
 /* Function Prototypes. */