The parser for custom pragmas has been moved into it's own
module and a data type for custom pragmas has been added.

In Haskell type variables in expression type signatures do not
refer to the type variables in the function's type signature.
If the type signature is introduced artificially by the inliner
(see ec9047a7), type variables are still scoped.

Due to the lack of type inference, the return type of helper
functions is not known by the compiler. There are some cases
where Coq cannot infer their return type either (see #11).
We can help Coq to infer the types of helper functions by
annotating the recursive calls with the return type provided
by the user.