Add ``--with-platlibdir`` option to the configure script: name of the
platform-specific library directory, stored in the new :attr:`sys.platlibdir`
attribute. It is used to build the path of platform-specific dynamic libraries
and the path of the standard library. It is equal to ``"lib"`` on most
platforms. On Fedora and SuSE, it is equal to ``"lib64"`` on 64-bit platforms.
Patch by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner.
