Remove the binding optimization from all but the modern build.

Former-commit-id: 1023ccc976e180425dabaa1b61e873e542aa3c2a

dist/lodash.underscore.js

@@ -56,9 +56,6 @@
   /** Used to match "interpolate" template delimiters */
   var reInterpolate = /<%=([\s\S]+?)%>/g;
 
-  /** Used to detect functions containing a `this` reference */
-  var reThis = (reThis = /\bthis\b/) && reThis.test(function() { return this; }) && reThis;
-
   /** Used to ensure capturing order of template delimiters */
   var reNoMatch = /($^)/;
 
@@ -126,7 +123,6 @@
       clearTimeout = window.clearTimeout,
       concat = arrayProto.concat,
       floor = Math.floor,
-      fnToString = Function.prototype.toString,
       hasOwnProperty = objectProto.hasOwnProperty,
       push = arrayProto.push,
       propertyIsEnumerable = objectProto.propertyIsEnumerable,
@@ -3481,7 +3477,7 @@
         return result;
       };
     }
-    if (typeof thisArg == 'undefined' || (reThis && !reThis.test(fnToString.call(func)))) {
+    if (typeof thisArg == 'undefined') {
       return func;
     }
     if (argCount === 1) {