Use clang compilation instead of lli-interpreting bitcode in cmake tests

- this fixes ARM builds for the time being, will have to be fixed
  for cross-compilation
Fix issue #119

Add environment variables (POCL_BUILDING & OCL_ICD_VENDORS) into
the test-running environment via CTestCustom.cmake.
Merge pull request #120 from franz/cmake

Cmake fixes
Tweaks to CHANGES.
CHANGES: Added the new bitcode linker.
Release notes.
Release version tagging. Disallow LLVM 3.6.
Several packaging issues revealed by 'make distcheck' fixed.
Release notes.
Fix CMake build on ARM. Issue #119.
Yet more distcheck fixes.
Some more fixes for issues found by distcheck
Started 0.11 development.
Merge remote-tracking branch 'pocl/master' into hpx