[unittests] Do not use llvm::sort in googlemock

[dberris]

Summary

This reverts r329475 which applied to googlemock. This change makes the
googlemock implementation in LLVM dependent on LLVM unnecessarily.

[echristo]

LGTM.

llvm/utils/unittest/googlemock/include/gmock/gmock-matchers.h

virtual void DescribeNegationTo(::std::ostream* os) const {
       matcher_.DescribeNegationTo(os);
     }
 
     virtual bool MatchAndExplain(LhsContainer lhs,
                                  MatchResultListener* listener) const {
       LhsStlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
       ::std::vector<LhsValue> sorted_container(lhs_stl_container.begin(),
                                                lhs_stl_container.end());
-      ::llvm::sort(
+      ::std::sort(
            sorted_container.begin(), sorted_container.end(), comparator_);
 
       if (!listener->IsInterested()) {
         // If the listener is not interested, we do not need to
         // construct the inner explanation.
         return matcher_.Matches(sorted_container);
       }