update fail_db for 3.6
removed 'llvm/Config/config.h' from cbackend.cpp build for LLVM 3.5+
Merge pull request #829 from ncos/knc_faildb

update fail_db for 3.6
Merge pull request #830 from ncos/ispc_build_fails

removed 'llvm/Config/config.h' from cbackend.cpp build for LLVM 3.5+
Merge branch 'master' of https://github.com/ncos/ispc into remove-support-for-old-llvm
remover LLVM 3_1 from cbackend.cpp