OCL compiler new flags - see notes

1. Added GMX_OCL_DUMP_INTERM_FILES - dump intermediate files for OpenCL
build:
- .IL/.ISA files for AMD
- .ptx file for NVIDIA
Ignored if caching is ON.
2. Added GMX_OCL_VERBOSE - prints extra info in build log.
Available only for NVIDIA.
Ignored if writing the log is disabled (see GMX_OCL_DUMP_LOG)
3. Renamed OCL_JIT_DUMP_FILE to GMX_OCL_DUMP_LOG - if defined, it forces
dumping OpenCL build log to file.