Added sys_physzero library call for corresponding system call; modified

system-printf() so it returns number of characters printed (for use in
smart formatting)

lib/syslib/Makefile

@@ -45,6 +45,7 @@ OBJECTS	= \
 	$(LIBSYS)(sys_signalrm.o) \
 	$(LIBSYS)(sys_flagalrm.o) \
 	$(LIBSYS)(sys_syncalrm.o) \
+	$(LIBSYS)(sys_physzero.o) \
 	$(LIBSYS)(taskcall.o) \
 
 $(LIBSYS):	$(OBJECTS)
@@ -165,6 +166,9 @@ $(LIBSYS)(sys_flagalrm.o):	sys_flagalrm.c
 $(LIBSYS)(sys_syncalrm.o):	sys_syncalrm.c
 	$(CC1) sys_syncalrm.c
 
+$(LIBSYS)(sys_physzero.o):	sys_physcp.c
+	$(CC1) sys_physzero.c
+
 $(LIBSYS)(taskcall.o):	taskcall.c
 	$(CC1) taskcall.c