Utility script to create release archive

- only include files known to git.
- includes all submodules.
- version extracted from BKE_blender.h for naming.
- MD5 checksum generated.
- 'make tbz' convenience target.

Script by Dan McGrath with own minor edits.

GNUmakefile

@@ -192,8 +192,8 @@ help:
 	@echo ""
 	@echo "Utilities (not associated with building blender)"
 	@echo "  * icons    - updates PNG icons from SVG files."
-	@echo "  * tbz      - create a compressed svn export 'blender_archive.tar.bz2'"
-	@echo "  * update   - updates git and all submodules
+	@echo "  * tgz      - create a compressed archive of the source code."
+	@echo "  * update   - updates git and all submodules"
 	@echo ""
 	@echo "Documentation Targets (not associated with building blender)"
 	@echo "  * doc_py   - generate sphinx python api docs"
@@ -361,11 +361,8 @@ check_descriptions:
 # Utilities
 #
 
-tbz:
-	svn export . blender_archive
-	tar cjf blender_archive.tar.bz2 blender_archive/
-	rm -rf blender_archive/
-	@echo "blender_archive.tar.bz2 written"
+tgz:
+	./build_files/utils/build_tgz.sh
 
 icons:
 	"$(BLENDER_DIR)/release/datafiles/blender_icons_update.py"