[PATCH] Add start of user documentation for NVPTX

[Sean Silva]

  Looks good. I have added a couple suggestions but they are mostly minor.


================
Comment at: docs/NVPTXUsage.rst:19
@@ +18,3 @@
+
+**NOTE**: This document assumes a basic familiarity with CUDA and the PTX
+assembly language. Information about the CUDA Driver API and the PTX assembly
----------------
Sphinx has a ".. note::" construct which prints pretty. See r177775 for an example of its usage.

================
Comment at: docs/NVPTXUsage.rst:21-22
@@ +20,4 @@
+assembly language. Information about the CUDA Driver API and the PTX assembly
+language can be found in the `CUDA documentation
+<http://docs.nvidia.com/cuda/index.html>`_.
+
----------------
Please add this link to <http://llvm.org/docs/CompilerWriterInfo.html> (docs/CompilerWriterInfo.rst).


http://llvm-reviews.chandlerc.com/D600

BRANCH
  master

ARCANIST PROJECT
  llvm