Add: [OSX] Text layout using the native CoreText API.

By default, the native API will be used instead of ICU, but if ICU is
forced in using configure, it will take precedence.

config.lib

@@ -2890,10 +2890,22 @@ detect_fontconfig() {
 }
 
 detect_icu_layout() {
+	if [ "$with_cocoa" != "0" ] && [ "$with_icu_layout" = "1" ]; then
+		log 1 "checking icu-lx... OSX, skipping"
+		icu_layout_config=""
+		return 0
+	fi
+
 	detect_pkg_config "$with_icu_layout" "icu-lx" "icu_layout_config" "4.8" "1"
 }
 
 detect_icu_sort() {
+	if [ "$with_cocoa" != "0" ] && [ "$with_icu_sort" = "1" ]; then
+		log 1 "checking icu-i18n... OSX, skipping"
+		icu_sort_config=""
+		return 0
+	fi
+
 	detect_pkg_config "$with_icu_sort" "icu-i18n" "icu_sort_config" "4.8" "1"
 }