mel-versions: gettext 0.18.3 -> 0.18.3.1

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
setup-mel-builddir: drop toolchain-layer for now

We aren't supporting the toolchain on the target anyway, so having 4.6 isn't
a priority.

Signed-off-by: Christopher Larson <chris_larson@mentor.com>