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/native/dalvik_system_DexFile.cc b/runtime/native/dalvik_system_DexFile.cc
index 27f19a7..9f9d82b 100644
--- a/runtime/native/dalvik_system_DexFile.cc
+++ b/runtime/native/dalvik_system_DexFile.cc
@@ -391,7 +391,7 @@
   // Check if we have an odex file next to the dex file.
   std::string odex_filename(DexFilenameToOdexFilename(filename, kRuntimeISA));
   std::string error_msg;
-  UniquePtr<const OatFile> oat_file(OatFile::Open(odex_filename, odex_filename, NULL, false,
+  std::unique_ptr<const OatFile> oat_file(OatFile::Open(odex_filename, odex_filename, NULL, false,
                                                   &error_msg));
   if (oat_file.get() == nullptr) {
     if (kVerboseLogging) {