gdbm.ffi: fix DLL name on Windows
gdbm.ffi: fix DLL name on Windows

erg/factor,erg/factor,mcandre/factor,kingcons/factor,erg/factor,mcandre/factor,kingcons/factor,mcandre/factor,mcandre/factor,erg/factor,kingcons/factor,mcandre/factor,mcandre/factor,erg/factor,erg/factor,mcandre/factor,kingcons/factor,erg/factor