Remove platform stlport from frameworks/rs.

The platform libRScpp tests should have been moved over when I moved
the library.

The HelloComputeNDK test should have always been built with the NDK,
since it is testing the NDK library.

Bug: 15193147
Change-Id: I419837505b9ead3c24b5674ea73e52da7739e162
3 files changed