Fix for DWARF debug info generation pipeline

Applies to LLVM-3.4, -3.5 and -trunk builds of ISPC
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
cast_sext/sext, i64 (l)shl/r and mul
added debug helpers for knc-i1x16.h
Merge branch 'knc-backend-merge' of https://github.com/ncos/ispc into knc-backend-merge
reduce_add_int8/16 implementation fixed
fixed lshr (i64 ...) function implementation
fial_db.txt refresh
Merge pull request #912 from ncos/knc-backend-merge

Knc backend merge
Fail_db update
Merge pull request #913 from Vsevolod-Livinskij/fail_db_update

Fail_db update
Added cstdlib include

the atoi and other functions were not transitively included under clang/llvm3.5
Merge pull request #914 from hansbogert/master

Added cstdlib include