panic() cleanup.

this change
   - makes panic() variadic, doing full printf() formatting -
     no more NO_NUM, and no more separate printf() statements
     needed to print extra info (or something in hex) before panicing
   - unifies panic() - same panic() name and usage for everyone -
     vm, kernel and rest have different names/syntax currently
     in order to implement their own luxuries, but no longer
   - throws out the 1st argument, to make source less noisy.
     the panic() in syslib retrieves the server name from the kernel
     so it should be clear enough who is panicing; e.g.
         panic("sigaction failed: %d", errno);
     looks like:
         at_wini(73130): panic: sigaction failed: 0
         syslib:panic.c: stacktrace: 0x74dc 0x2025 0x100a
   - throws out report() - printf() is more convenient and powerful
   - harmonizes/fixes the use of panic() - there were a few places
     that used printf-style formatting (didn't work) and newlines
     (messes up the formatting) in panic()
   - throws out a few per-server panic() functions
   - cleans up a tie-in of tty with panic()

merging printf() and panic() statements to be done incrementally.

include/minix/const.h

@@ -60,7 +60,6 @@
 #define BYTE            0377	/* mask for 8 bits */
 #define READING            0	/* copy data to user */
 #define WRITING            1	/* copy data from user */
-#define NO_NUM        0x8000	/* used as numerical argument to panic() */
 #define NIL_PTR   (char *) 0	/* generally useful expression */
 #define HAVE_SCATTERED_IO  1	/* scattered I/O is now standard */