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/log/Makefile

@@ -0,0 +1,46 @@
+# Makefile for log driver
+DRIVER = log
+
+# directories
+u = /usr
+i = $u/include
+s = $i/sys
+m = $i/minix
+d = ..
+
+# programs, flags, etc.
+MAKE = exec make
+CC =	exec cc
+CFLAGS = -I$i
+LDFLAGS = -i
+LIBS = -lsys -lutils
+
+OBJ = log.o 
+LIBDRIVER = $d/libdriver/driver.o
+
+
+# build local binary
+all build:	$(DRIVER)
+$(DRIVER):	$(OBJ) $(LIBDRIVER)
+	$(CC) -o $@ $(LDFLAGS) $(OBJ) $(LIBDRIVER) $(LIBS)
+	install -S 64w $(DRIVER)
+
+$(LIBDRIVER): 
+	cd $d/libdriver && $(MAKE) 
+
+# install with other drivers
+install:	/usr/sbin/drivers/$(DRIVER)
+/usr/sbin/drivers/$(DRIVER):	$(DRIVER)
+	install -o root -cs $? $@
+
+# clean up local files
+clean:
+	rm -f $(DRIVER) *.o *.bak 
+
+
+depend: 
+	/usr/bin/mkdep "$(CC) -E $(CPPFLAGS)" *.c ../libdriver/*.c > .depend
+
+# Include generated dependencies.
+include .depend
+