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.

kernel/debug.h

@@ -60,20 +60,18 @@
 
 #if DEBUG_VMASSERT
 #define vmassert(t) { \
-	if(!(t)) { minix_panic("vm: assert " #t " failed in " __FILE__, __LINE__); } }
+	if(!(t)) { panic("kernel:%s:%d: assert %s failed", __FILE__, __LINE__, #t); } }
 #else
 #define vmassert(t) { }
 #endif
 
 #define NOT_REACHABLE	do {						\
-	printf("NOT_REACHABLE at %s:%d\n", __FILE__, __LINE__);	\
-	minix_panic("execution at an unexpected location\n", NO_NUM);	\
+	panic("NOT_REACHABLE at %s:%d", __FILE__, __LINE__);	\
 	for(;;);							\
 } while(0)
 
 #define NOT_IMPLEMENTED do {	\
-		printf("NOT_IMPLEMENTED at %s:%d\n", __FILE__, __LINE__); \
-		minix_panic("NOT_IMPLEMENTED", NO_NUM); \
+		panic("NOT_IMPLEMENTED at %s:%d", __FILE__, __LINE__); \
 } while(0)
 
 #ifdef CONFIG_BOOT_VERBOSE