Build: Put all AMD modules in "src/" in strict mode

Fixes gh-3073

src/event/ajax.js

@@ -3,6 +3,8 @@ define( [
 	"../event"
 ], function( jQuery ) {
 
+"use strict";
+
 // Attach a bunch of functions for handling common AJAX events
 jQuery.each( [
 	"ajaxStart",

src/event/alias.js

@@ -5,6 +5,8 @@ define( [
 	"./trigger"
 ], function( jQuery ) {
 
+"use strict";
+
 jQuery.each( ( "blur focus focusin focusout resize scroll click dblclick " +
 	"mousedown mouseup mousemove mouseover mouseout mouseenter mouseleave " +
 	"change select submit keydown keypress keyup contextmenu" ).split( " " ),

src/event/focusin.js

@@ -7,6 +7,8 @@ define( [
 	"./trigger"
 ], function( jQuery, dataPriv, support ) {
 
+"use strict";
+
 // Support: Firefox <=44
 // Firefox doesn't have focus(in | out) events
 // Related ticket - https://bugzilla.mozilla.org/show_bug.cgi?id=687787

src/event/support.js

@@ -2,6 +2,8 @@ define( [
 	"../var/support"
 ], function( support ) {
 
+"use strict";
+
 support.focusin = "onfocusin" in window;
 
 return support;

src/event/trigger.js

@@ -8,6 +8,8 @@ define( [
 	"../event"
 ], function( jQuery, document, dataPriv, acceptData, hasOwn ) {
 
+"use strict";
+
 var rfocusMorph = /^(?:focusinfocus|focusoutblur)$/;
 
 jQuery.extend( jQuery.event, {