. new kernel call sysctl for generic unprivileged system operations;

now used for printing diagnostic messages through the kernel message
   buffer. this lets processes print diagnostics without sending messages
   to tty and log directly, simplifying the message protocol a lot and
   reducing difficulties with deadlocks and other situations in which
   diagnostics are blackholed (e.g. grants don't work). this makes
   DIAGNOSTICS(_S), ASYN_DIAGNOSTICS and DIAG_REPL obsolete, although tty
   and log still accept the codes for 'old' binaries. This also simplifies
   diagnostics in several servers and drivers - only tty needs its own
   kputc() now.
 . simplifications in vfs, and some effort to get the vnode references
   right (consistent) even during shutdown. m_mounted_on is now NULL
   for root filesystems (!) (the original and new root), a less awkward
   special case than 'm_mounted_on == m_root_node'. root now has exactly
   one reference, to root, if no files are open, just like all other
   filesystems. m_driver_e is unused.

kernel/proto.h

@@ -93,6 +93,9 @@ _PROTOTYPE( void check_runqueues_f, (char *file, int line) );
 _PROTOTYPE( int verify_grant, (endpoint_t, endpoint_t, cp_grant_id_t, vir_bytes,
 	int, vir_bytes, vir_bytes *, endpoint_t *));
 
+/* system/do_sysctl.c */
+_PROTOTYPE( int do_sysctl, (message *m));
+
 #if SPROFILE
 /* profile.c */
 _PROTOTYPE( void init_profile_clock, (u32_t)				);