Retire debian/ directory.

The official maintainer is keeping up-to-date quite well, and now
the older Debian is supported with backports.org, there is no reason
for me to keep debian/ directory around here.

I have not been building and publishing debs since 1.0.4 anyway.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Makefile

@@ -489,12 +489,6 @@ dist: git.spec git-tar-tree
 rpm: dist
 	$(RPMBUILD) -ta $(GIT_TARNAME).tar.gz
 
-deb: dist
-	rm -rf $(GIT_TARNAME)
-	$(TAR) zxf $(GIT_TARNAME).tar.gz
-	dpkg-source -b $(GIT_TARNAME)
-	cd $(GIT_TARNAME) && fakeroot debian/rules binary
-
 ### Cleaning rules
 
 clean:
@@ -504,8 +498,6 @@ clean:
 	rm -f *.spec *.pyc *.pyo */*.pyc */*.pyo
 	rm -rf $(GIT_TARNAME)
 	rm -f $(GIT_TARNAME).tar.gz git-core_$(GIT_VERSION)-*.tar.gz
-	rm -f git-core_$(GIT_VERSION)-*.dsc
-	rm -f git-*_$(GIT_VERSION)-*.deb
 	$(MAKE) -C Documentation/ clean
 	$(MAKE) -C templates clean
 	$(MAKE) -C t/ clean