Add gettext to Travis build

Signed-off-by: Craig Robbins <kde.psych@gmail.com>
Fix Belarusian translation header

Signed-off-by: Craig Robbins <kde.psych@gmail.com>
Add (optional) client-side saving of server map to disk
Tweak core.serialize

This adds proper support for nested tables and improves performance a bit.
Add strict module

Also fix leaking globals found by it.
Fix wallmounted mesh rotations
Clean up rollback
Fix raillike bug (currently manifests itself on Android), and minor improvement to readability.

NB: Minor edits to patch made by Zeno- (int to short and minor formatting)
Fix leaking global in texture pack menu
Simplify loading of Android version of menu
Mgv5 get ground level at point function. Fast spawn player version
Mgv5 1 up 1 down overgeneration for biome surface continuity
Optimise getTileInfo()

getTileInfo() ~1.5x faster
getSmoothLight ~2.0x faster
Optimise functions from CNodeDefManager and VoxelManipulator

CNodeDefManager::get()
VoxelManipulator::addArea()
Handle anisotropic filtering on the wield mesh in a complicated way

(See the comment at wieldmesh.cpp:299 for the reasoning behind this.)