This option had been broken for several reasons:
* The getstyle utility does not replace the #usergnusteppath# macro which
was passed to it by the menu.
* When processing the USER_THEMES_DIR macro, the menu inserts a space
afterwards, and so the directory and filename were passed to getstyle
as two separate arguments.
* It used the old, pre-0.50.0 theme format.
By using the -p option to getstyle, we can avoid these issues, as we don't
need to specify the directory *and* it uses the 'new' (since 1999) themepack
format.
We remove the macros LOCAL_THEMES_DIR, LOCAL_STYLES_DIR,
LOCAL_ICON_SETS_DIR, and LOCAL_BACKGROUNDS_DIR.
They were only referenced in the Debian patch 54_Debian_wmmacros.diff, which
set them to /usr/local/share/WindowMaker/{Themes,Styles,etc.}.
In a default installation, THEMES_DIR, STYLES_DIR, etc. coincide exactly
with these paths. In a Debian installation (which defaults to /usr/share
instead of /usr/local/share), it seems unlikely that a user would have these
files in both locations.
