bump(toolchain): sync with upstream

Packages updated:
  sys-devel/binutils
  sys-devel/gcc
  sys-devel/gdb
  sys-kernel/linux-headers
  sys-libs/glibc
bump(eclass): Update eclasses used by toolchain ebuilds.

Sync with upstream, but only a small set of eclasses just to reduce the
chance of surprises. A full sync of all eclasses will come later.
Merge pull request #15 from marineam/toolchain

Toolchain updates