bug fix - #742 JQueryAjaxSettings does not allow contentType set to false

jquery/jquery-tests.ts

@@ -2302,3 +2302,17 @@ $.when("asdf", "jkl;").done(x => x.length, x=> x.length);
 var f1 = $.when("fetch"); // Is type JQueryPromise<string>
 var f2: JQueryPromise<string[]> = f1.then(s => [s, s]);
 var f3: JQueryPromise<number> = f2.then(v => 3);
+
+// ISSUE: https://github.com/borisyankov/DefinitelyTyped/issues/742
+// http://stackoverflow.com/questions/5392344/sending-multipart-formdata-with-jquery-ajax#answer-5976031
+$.ajax({
+    url: 'php/upload.php',
+    data: {},
+    cache: false,
+    contentType: false,
+    processData: false,
+    type: 'POST',
+    success: function (data) {
+        alert(data);
+    }
+});

jquery/jquery.d.ts

@@ -25,7 +25,9 @@ interface JQueryAjaxSettings {
     cache?: boolean;
     complete? (jqXHR: JQueryXHR, textStatus: string);
     contents?: { [key: string]: any; };
-    contentType?: string;
+    //According to jQuery.ajax source code, ajax's option actually allows contentType to set to "false"
+    // https://github.com/borisyankov/DefinitelyTyped/issues/742
+    contentType?: any;
     context?: any;
     converters?: { [key: string]: any; };
     crossDomain?: boolean;