Increase performance of getLight() by at least 2x

Leads to the following increases:
getSmoothLight() approx.     40% increase
getTileInfo() approx.        25% increase
MapBlockMesh::MapBlockMesh() 25-30%
Ignore .name directories and files

Signed-off-by: Craig Robbins <kde.psych@gmail.com>
Rewrite fs:GetDirListing(file) by kahrl