[PATCH] cogito: "make clean" fails if make is not GNU make

GNU make automatically passes the -w option when -C is used.  On
systems where GNU make is called "gmake", invoking "make" from within
the Makefile will run a make that may not understand that option:

$ gmake -C Documentation/ clean
gmake: Entering directory `/usr/home/dennis/tmp/cogito/Documentation'
make -C tutorial-script clean
make: don't know how to make w. Stop
gmake: *** [clean] Error 2

Signed-off-by: Dennis Stosberg <redacted>
---
 Documentation/Makefile |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/Makefile b/Documentation/Makefile
index 36295a7..b48e49c 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile

@@ -60,10 +60,10 @@ install-html: html
 	$(INSTALL) $(DOC_HTML) $(DESTDIR)/$(htmldir)
 
 test:
-	make -C tutorial-script test
+	$(MAKE) -C tutorial-script test
 
 clean:
-	make -C tutorial-script clean
+	$(MAKE) -C tutorial-script clean
 	rm -f *.xml *.html *.pdf *.1 *.7 cg*.[17].txt $(PACKAGE).7.txt
 
 .PRECIOUS: cg%.txt introduction.txt

-- 
1.4.1.rc1.ge6b53