Now we have a proper C++ library, use std::unique_ptr.

Also remove the Android.libcxx.mk and other bits of stlport compatibility
mechanics.

Change-Id: Icdf7188ba3c79cdf5617672c1cfd0a68ae596a61
diff --git a/runtime/trace.cc b/runtime/trace.cc
index b85eb7e..d53b369 100644
--- a/runtime/trace.cc
+++ b/runtime/trace.cc
@@ -119,7 +119,7 @@
 
 Trace* volatile Trace::the_trace_ = NULL;
 pthread_t Trace::sampling_pthread_ = 0U;
-UniquePtr<std::vector<mirror::ArtMethod*> > Trace::temp_stack_trace_;
+std::unique_ptr<std::vector<mirror::ArtMethod*>> Trace::temp_stack_trace_;
 
 static mirror::ArtMethod* DecodeTraceMethodId(uint32_t tmid) {
   return reinterpret_cast<mirror::ArtMethod*>(tmid & ~kTraceMethodActionMask);
@@ -339,7 +339,7 @@
   runtime->GetThreadList()->SuspendAll();
 
   // Open trace file if not going directly to ddms.
-  UniquePtr<File> trace_file;
+  std::unique_ptr<File> trace_file;
   if (!direct_to_ddms) {
     if (trace_fd < 0) {
       trace_file.reset(OS::CreateEmptyFile(trace_filename));