Added args to lock() and unlock() to tell them apart, for use

when lock timing is enabled in minix/config.h.

Added phys_zero() routine to klib386.s that zeroes a range of memory, and
added corresponding system call.

kernel/debug.h

@@ -0,0 +1,16 @@
+
+#ifndef DEBUG_H
+#define DEBUG_H
+
+#include <minix/config.h>
+
+#if ENABLE_LOCK_TIMING
+_PROTOTYPE( void timer_start, (int cat, char *name) );
+_PROTOTYPE( void timer_end, (int cat) );
+#endif
+
+#if ENABLE_K_DEBUGGING 					/* debugging */
+_PROTOTYPE( void check_runqueues, (char *when) );
+#endif
+
+#endif	/* DEBUG_H */