Add support for the PTX compilation API

[eyalroz]

Somehow, NVIDIA's separate library for compiling PTX code into SASS escaped me...

It's documented at:

https://docs.nvidia.com/cuda/ptx-compiler-api/index.html

and we should definitely add support for it.

There's a "handle" type, similar to an NVRTC "program"; and the functions are:

Functions:

• nvPTXCompilerCompile ( nvPTXCompilerHandle compiler, int numCompileOptions, const char** compileOptions )
  Compile a PTX program with the given compiler options.
• nvPTXCompilerCreate ( nvPTXCompilerHandle* compiler, size_t ptxCodeLen, const char* ptxCode )
  Obtains the handle to an instance of the PTX compiler initialized with the given PTX program ptxCode.
• nvPTXCompilerDestroy ( nvPTXCompilerHandle* compiler )
  Destroys and cleans the already created PTX compiler.
• nvPTXCompilerGetCompiledProgram ( nvPTXCompilerHandle compiler, void* binaryImage )
  Obtains the image of the compiled program.
• nvPTXCompilerGetCompiledProgramSize ( nvPTXCompilerHandle compiler, size_t* binaryImageSize )
  Obtains the size of the image of the compiled program.
• nvPTXCompilerGetErrorLog ( nvPTXCompilerHandle compiler, char* errorLog )
  Query the error message that was seen previously for the handle.
• nvPTXCompilerGetErrorLogSize ( nvPTXCompilerHandle compiler, size_t* errorLogSize )
  Query the size of the error message that was seen previously for the handle.
• nvPTXCompilerGetInfoLog ( nvPTXCompilerHandle compiler, char* infoLog )
  Query the information message that was seen previously for the handle.
• nvPTXCompilerGetInfoLogSize ( nvPTXCompilerHandle compiler, size_t* infoLogSize )
  Query the size of the information message that was seen previously for the handle.

and a version function:

• nvPTXCompileResult nvPTXCompilerGetVersion] ( unsigned int* major, unsigned int* minor )

Need to think about where that's going to go, namespace-wise (and reconsider the same for NVRTC - if it even has a version number).

[eyalroz]

We could have a single interface for CUDA C++ and for PTX, and this makes extra sense because both can be compiled into SASS; but - the options for PTX compilations are not quite the same PTX, CUDA C++.