Neon: Finalize intrinsics implementation - Remove gas-preprocessor.pl. None of the compilers that can build the new intrinsics implementation require gas-preprocessor.pl (tested with Xcode and with Clang 3.9+ for Linux.) - Document that Xcode 6.3.x or later is now required for iOS builds (older versions of Xcode do not have a full set of Neon intrinsics.) - Add a change log entry. - Do not enable the ASM CMake language unless NEON_INTRINSICS is false. - Add a Clang/Arm64 test to .travis.yml in order to test the new intrinsics implementation. Closes #455