Removed tools/gdb from "make all" target.  Added make target "gdbtools"
in toplevel directory instead.  Removed astest.c from tools/gdb because
it is no longer relevant.
diff --git a/Makefile b/Makefile
index c4bb10c..249a067 100644
--- a/Makefile
+++ b/Makefile
@@ -148,6 +148,9 @@
 subdirs:
 		@for dir in $(SUBDIRS) ; do $(MAKE) -C $$dir || exit 1 ; done
 
+gdbtools:
+		$(MAKE) -C tools/gdb || exit 1
+
 depend dep:
 		@for dir in $(SUBDIRS) ; do $(MAKE) -C $$dir .depend ; done