WINGs: Rename copy_file() to wcopy_file()

...in order to avoid clashes that happen during compilation of
wmakerconf.

This is a new function in WINGs, so renaming it at this point is
not a big deal.

Thanks to Rodolfo García for the heads up.

WINGs/wcolorpanel.c

@@ -2924,7 +2924,7 @@ static void customPaletteMenuNewFromFile(W_ColorPanel * panel)
 
 		/* Copy image to $(gnustepdir)/Library/Colors/ &
 		 * Add filename to history menu */
-		if (copy_file(panel->configurationPath, filepath, filename) == 0) {
+		if (wcopy_file(panel->configurationPath, filepath, filename) == 0) {
 
 			/* filepath is a "local" path now the file has been copied */
 			wfree(filepath);