Add ConstantFP::getDoubleValue method and the corresponding C API.
[OCaml] Add float_of_const for llvm::ConstantFP::getDoubleValue.
[C Api] Add various functions for terminator and branch instructions.
[OCaml] Add various functions for terminator and branch instructions.
[OCaml] Add utilities function related to terminator and branches.
[OCaml] Expose some documentation in ocamldoc.