wmgenmenu: Fix "Save Theme"

Dario Niedermann reported on 27.11.2011:

       Selecting "Save Theme" from WMaker's root menu results in dialog box
       asking for theme name, but then nothing is saved.

       This feature used to work in 0.92.0.

and the reason for it (if he uses a WMRootMenu generated by wmgenmenu) is
the incorrect use of the option "-t" instead of "-p" to getstyle.

Furthermore, let the invocation of getstyle reflect the new default location
for the themes.

util/wmgenmenu.c

@@ -243,8 +243,7 @@ int main(int argc, char *argv[])
 	L2Menu = WMCreatePLArray(
 		WMCreatePLString(_("Save Theme")),
 		WMCreatePLString("SHEXEC"),
-		WMCreatePLString("getstyle -t $HOME/GNUstep/Library/WindowMaker/Themes/"
-			"\"%a(Theme name, Name to save theme as)\""),
+		WMCreatePLString("getstyle -p \"%a(Theme name, Name to save theme as)\""),
 		NULL
 	);
 	WMAddToPLArray(L1Menu, L2Menu);