Fix double free bug when server is shut down

Thanks @oleastre
Update Indonesian Language

Signed-off-by: Craig Robbins <kde.psych@gmail.com>
Fix indonesian language errors

Errors found by @Sokomine.
Remove unused rangelim function (the macro still exists)
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)
Merge branch 'master' of https://github.com/minetest/minetest into gsmapper