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/java_lang_VMClassLoader.cc b/runtime/native/java_lang_VMClassLoader.cc
index cb8e623..f2b8a03 100644
--- a/runtime/native/java_lang_VMClassLoader.cc
+++ b/runtime/native/java_lang_VMClassLoader.cc
@@ -73,12 +73,12 @@
   const DexFile* dex_file = path[index];
   const std::string& location(dex_file->GetLocation());
   std::string error_msg;
-  UniquePtr<ZipArchive> zip_archive(ZipArchive::Open(location.c_str(), &error_msg));
+  std::unique_ptr<ZipArchive> zip_archive(ZipArchive::Open(location.c_str(), &error_msg));
   if (zip_archive.get() == nullptr) {
     LOG(WARNING) << "Failed to open zip archive '" << location << "': " << error_msg;
     return NULL;
   }
-  UniquePtr<ZipEntry> zip_entry(zip_archive->Find(name.c_str(), &error_msg));
+  std::unique_ptr<ZipEntry> zip_entry(zip_archive->Find(name.c_str(), &error_msg));
   if (zip_entry.get() == NULL) {
     return NULL;
   }