In order to achieve efficient code generation using GHC.Generics,
the transformations between the original representation and GHC.Generics
representation must be able to optimize away. While inlining of these
methods is necessary for efficient code, it is not sufficient.
This patch marks these methods as INLINABLE so that techniques that
do support efficient code generation can work across module boundaries
when from/to might not have been considered inlinable on their own by