hilapp is the hila preprocessor.  It is built with Clang libtooling library, see 
https://clang.llvm.org/docs/LibTooling.html

For compatibility with Clang/LLVM, hilapp source (contents of this directory) is 
licenced with Apache 2.0 licence with LLVM Exceptions (see LICENCE),
in addition to the GPLv2 licence.
