Fail_db update for icc.v15
Merge pull request #875 from Vsevolod-Livinskij/fail_db_update

Fail_db update.
PTX support is off by default.
Fix to make it compile with PTX support off by default.
Build clang with NVPTX support.
Merge pull request #876 from dbabokin/ptx_off

PTX support refinement