Use a internal LLVM library instead of llvm-hs

[Ailrun]

Is your feature request related to a problem? Please describe.
With llvm-hs library, it's hard to change stack LTS while preserving the version of LLVM.
Further more, if the library makes it harder to share similar structures (like identifiers) between non-LLVM codes and LLVM codes.

Describe the solution you'd like
Use a internal LLVM library which shares basic data types with other codes.

Describe alternatives you've considered
Use data types of llvm-hs in other code bases. Sadly, with this solution, it is still hard to update stack LTS independently.

Additional context
It should be carefully inspected that how hard to make a internal library for LLVM.

[Ailrun]

Name candidates

• llvm-syntax