Revert "Fix #13291, no longer need the functionish-regex guard."

Turns out this is still needed by Safari 5.1, which we're still supporting.

This reverts commit c4b1da40.

src/core.js

@@ -411,7 +411,8 @@ jQuery.extend({
 		if ( obj == null ) {
 			return String( obj );
 		}
-		return typeof obj === "object" ?
+		// Support: Safari <5.1 (functionish RegExp)
+		return typeof obj === "object" || typeof obj === "function" ?
 			class2type[ core_toString.call(obj) ] || "object" :
 			typeof obj;
 	},