Fix the Makefile.in to properly clean the user_modules tree.
drwxr-xr-x - citadel
drwxr-xr-x - contrib
drwxr-xr-x - ctdlphp
drwxr-xr-x - ctdlsalearn
drwxr-xr-x - ctdlsh
drwxr-xr-x - libcitadel
drwxr-xr-x - webcit