New autoconf test to determine LIBMESH_DIM
New autoconf test to determine LIBMESH_DIM

This is useful because we can then SKIP tests that require
a certain LIBMESH_DIM and that LIBMESH_DIM is not present
in the configured LIBMESH_DIR.

cahaynes/grins,vikramvgarg/grins,cahaynes/grins,cahaynes/grins,vikramvgarg/grins,nicholasmalaya/grins,nicholasmalaya/grins,cahaynes/grins,cahaynes/grins,nicholasmalaya/grins,vikramvgarg/grins,vikramvgarg/grins,vikramvgarg/grins,cahaynes/grins,vikramvgarg/grins,nicholasmalaya/grins