gcc48: always link libgcc on netbsd (GCC r248037,
applied to GCC 8 and above - thanks Krister Walfridsson)

libstdc++: if it thinks vswprintf is broken, don't block the
entire definition of to_string, just that of to_wstring. backport
of GCC r223830 already applied to GCC 4.9. this applies to netbsd-6-0.

Doesn't fix any build I wanted to fix, but it does get the build
of LLVM4.x further on netbsd-6-0. maybe there's an odd package that
could benefit from it.

bump PKGREVISION.

(maya)