Replace print()s with minetest.log() in builtin
Revert "Don't use msvc libs for mingw build"

This reverts commit 3985c01ad71159b888677d0fe2019d7a05debeed.
Handle blank blocks in database

Fix screwed-up indentation
Do the same for LevelDB interface
Fix multicaller support in RequestQueue
Add missing RequestQueue doc
Fix Result of processed Request was written to invalid (non existent) ResultQueue if requesting thread timed out before