Import GCC 5.0 snapshot as wip/gcc50snapshot.

The GNU Compiler Collection (GCC) includes front ends for C, C++, Objective-C,
Fortran, Java, and Go, as well as libraries for these languages (libstdc++,
libgcj,...). This package provides the snapshot release of version 5.0.

On NetBSD a working cabsl function must be present in libm to build gfortran.
This has been added to -current on 2014/10/10 and to NetBSD7 on 2014/10/13.