- Member functions represented by member_function<>
    specific type in the backend.
  - Custom metadata to deal with overloads: argument names,
    display name, full display name, etc
  - Global access to metadata through entity name

When downloading LLVM precompiled installation make sure cppast is also
built with legacy GCC ABI to prevent ABI issues.

Some of these images have gcc/g++ not aliased to the right
version installed in the images (i.e. the image gcc8 has gcc-8 installed
but gcc is gcc-7, not an alias to gcc-8). Since conan uses CC
environment variable to set the profile settings.compiler, we need
to make sure CC is aliased to the right compiler version

The package version file generation assumes VERSION variable
set in the project, but we forgot to set it for the cmake project
using to host-compile the tool when cross-compiling tinyrefl

This commit fixes the codegen tool so that the macro-based generated
code generates code compatible with types and expressions containing
commas, such as the type 'map<int, string>'. Now all metadata arguments
are enclosed by parens to make sure the values are expanded to the right
enclosing macro call.