GetProcAddress returns a pointer to some function. It can return
pointers to different functions, so it has to return something that is
suitable to store any pointer to function. Microsoft chose FARPROC,
which is int (WINAPI *)() on 32-bit Windows. The user is supposed to
know the signature of the function he requests and perform a cast
(which is a nop on this platform). The result is a pointer to function
with the required signature, which is bitwise equal to what
GetProcAddress returned.
However, gcc >= 8 warns about that.

Add a template parameter to do the cast inside the function and suppress
the warning there.