Build and installation procedure clean-up.
* jn/mediawiki-makefile-updates:
git-remote-mediawiki build: handle DESTDIR/INSTLIBDIR with whitespace
git-remote-mediawiki build: make 'install' command configurable
git-remote-mediawiki: honor DESTDIR in "make install"
git-remote-mediawiki: do not remove installed files in "clean" target