fix(angular.copy): clone regexp flags correctly

Closes angular#5781
Closes angular#8337

Author: shahata

src/Angular.js

@@ -775,7 +775,8 @@ function copy(source, destination, stackSource, stackDest) {
       } else if (isDate(source)) {
         destination = new Date(source.getTime());
       } else if (isRegExp(source)) {
-        destination = new RegExp(source.source);
+        destination = new RegExp(source.source, source.toString().match(/[^\/]*$/)[0]);
+        destination.lastIndex = source.lastIndex;
       } else if (isObject(source)) {
         var emptyObject = Object.create(Object.getPrototypeOf(source));
         destination = copy(source, emptyObject, stackSource, stackDest);

test/AngularSpec.js

@@ -55,6 +55,20 @@ describe('angular', function() {
       expect(copy(re) === re).toBeFalsy();
     });
 
+    it("should copy RegExp with flags", function() {
+      var re = new RegExp('.*', 'gim');
+      expect(copy(re).global).toBe(true);
+      expect(copy(re).ignoreCase).toBe(true);
+      expect(copy(re).multiline).toBe(true);
+    });
+
+    it("should copy RegExp with lastIndex", function() {
+      var re = /a+b+/g;
+      var str = 'ab aabb';
+      expect(re.exec(str)[0]).toEqual('ab');
+      expect(copy(re).exec(str)[0]).toEqual('aabb');
+    });
+
     it("should deeply copy literal RegExp", function() {
       var objWithRegExp = {
         re: /.*/