New log driver; buffers messages and makes them available to userland.

Added some fields in the generic device table to support this driver
using libdriver. Updated other drivers to fill these fields with nops
and NULLs.

drivers/memory/memory.c

@@ -56,7 +56,11 @@ PRIVATE struct driver m_dtab = {
   nop_cleanup,	/* no need to clean up */
   m_geometry,	/* memory device "geometry" */
   nop_stop,	/* no need to clean up on shutdown */
-  m_random, 	/* get randomness from kernel */
+  m_random, 	/* get randomness from kernel (alarm) */
+  nop_fkey,	/* ignore function key presses and CANCELs */
+  nop_cancel,
+  nop_select,
+  NULL
 };
 
 /* Buffer for the /dev/zero null byte feed. */