Sanitize calling sites of wDefaultsCheckDomains()

There is no point in having parameter in wDefaultsCheckDomains() and
not using it, so let's simply remove the parameter altogether and
avoid silly-looking things like

    wDefaultsCheckDomains("bla");

src/defaults.c

@@ -1209,7 +1209,7 @@ wReadStaticDefaults(WMPropList *dict)
 
 
 void
-wDefaultsCheckDomains(void *foo)
+wDefaultsCheckDomains(void)
 {
     WScreen *scr;
     struct stat stbuf;