Merge pull request #624 from ifilippov/fix1

patch for LLVM for fails on avx-x2 target
Merge pull request #626 from ifilippov/fix1

fix for ISPC for compfails at sse4-i8 and sse4-i16
Switching default compiler on Unix from g++ to clang++
Switch examples on Unix from using g++ to clang++
Fix problem with building ISPC by clang 3.4
Enable clang as default C++ compiler used by run_tests.py and perf.py
fail_db.txt update with fails with clang 3.3 as a C++ compiler for tests (Linux)
Update fail_db with new passes after change in trunk
Merge pull request #627 from dbabokin/clang_build

Switch over to clang as default C++ compiler for build and test
Fail_db update on Mac with clang 3.3 compiler
Merge pull request #628 from dbabokin/fail_db

Fail_db update on Mac with clang 3.3 compiler
Fix small typo for NEON targets in Target::SupportedTargets
Merge pull request #629 from mmp/typo

Fix small typo for NEON targets in Target::SupportedTargets
Merge pull request #630 from ifilippov/testing

new changes in test system
 added avx2-i64x4 and avx1.1-i64x4 targets
__masked_store_* uses vscatter now, and is thread-safe
Merge pull request #634 from egaburov/patch_knc

Making __masked_store_* thread-safe
removed LLVM_3_0 legacy part and changed copyright to 2013
Merge pull request #631 from egaburov/avx2-i64x4

 added avx2-i64x4 and avx1.1-i64x4 targets
Adding testing support for avx1.1-i64x4 and avx2-i64x4 targets