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/build/Android.executable.mk b/build/Android.executable.mk
index 683d91d..3c33975 100644
--- a/build/Android.executable.mk
+++ b/build/Android.executable.mk
@@ -100,12 +100,11 @@
   endif
 
   ifeq ($$(art_target_or_host),target)
-    include art/build/Android.libcxx.mk
+    include external/libcxx/libcxx.mk
     include $(BUILD_EXECUTABLE)
     ART_TARGET_EXECUTABLES := $(ART_TARGET_EXECUTABLES) $(TARGET_OUT_EXECUTABLES)/$$(LOCAL_MODULE)
   else # host
     LOCAL_IS_HOST_MODULE := true
-    include art/build/Android.libcxx.mk
     include $(BUILD_HOST_EXECUTABLE)
     ART_HOST_EXECUTABLES := $(ART_HOST_EXECUTABLES) $(HOST_OUT_EXECUTABLES)/$$(LOCAL_MODULE)
   endif