Merge pull request #903 from ncos/knc-backend-merge

Add several functions to knc.h
fixed ISPC compilation fail caused by the change of llvm::Value to llvm::Constant in DIBuilder member functions (LLVM commit 222070)
Merge pull request #906 from ncos/ispc_build_fails

fixed ISPC compilation fail caused by LLVM DIBuilder API change
Tracking LLVM trunk: SmallPtrSet changes
Merge pull request #908 from dbabokin/trunk

Tracking LLVM trunk: SmallPtrSet changes
Fix for DWARF debug info generation pipeline

Applies to LLVM-3.4, -3.5 and -trunk builds of ISPC
Build fix for LLVM trunk - changed include structure
Merge pull request #910 from dbabokin/trunk

Build fix for LLVM trunk - changed include structure
Merge pull request #911 from aguskov/master

Fix for DWARF debug info generation pipeline
Merge branch 'knc-backend-merge' of https://github.com/ncos/ispc into knc-backend-merge