Remove doc generation from Makefile

This was not maintained.

Makefile

@@ -19,19 +19,6 @@ clean:
 analyze:
 	scan-build scons mode=analyze
 
-# Make the doc using natualdocs.  On debian, we only have an old version
-# of naturaldocs available, where it is not possible to exclude files by
-# pattern.  I don't want to parse the C files (only the headers), so for
-# the moment I use a tmp file to copy the sources and remove the C files.
-# It's a bit ugly.
-.PHONY: doc
-doc:
-	rm -rf /tmp/goxel_src
-	cp -rf src /tmp/goxel_src
-	find /tmp/goxel_src -name '*.c' | xargs rm
-	mkdir -p doc ndconfig
-	naturaldocs -i /tmp/goxel_src -o html doc -p ndconfig
-
 # Targets to install/uninstall goxel and its data files on unix system.
 PREFIX ?= /usr/local