Show PTX and ISA from OpenCL kernel

1. Have JtR save a "binary" (actually PTX) of the kernel. This can be achieved by setting DUMP_BINARY environment variable. File name will be kernel's name plus a ".bin" extension, in current directory.
2. ptxas --gpu-name sm_52 foo_kernel.cl.bin -o foo.o
3. nvdisasm foo.o > foo.isa

Note: CUDA 7.0 ptxas complained about a 352.21 PTX file having "Unsupported .version 4.3; current version is '4.2'" but that can sometimes be worked around simply by editing it 😎

For AMD, use AMD_OCL_BUILD_OPTIONS_APPEND=-save-temps.