Allow use all 6 faces for special tiles.
Protocol version bump.
Add missing doc for minetest.get_us_time()
Remove invalid doc about minetest.get_time_us()
update games/default
Fix interlaced 3d mode second image being flipped on compiling against irrlicht >= 1.8
Fix only one texture being updated on window resize breaking sidebyside and topbottom 3d modes
fix fog flicker
fog fix 2.0
return more_threads=0 on windows
Merge remote-tracking branch 'minetest/master'

Conflicts:
	doc/lua_api.txt
	src/nodedef.cpp
Fixed minetest compatibility
remove noisy debug
Small lock optimize
Merge remote-tracking branch 'upstream/master' into octree

Conflicts:
	src/defaultsettings.cpp
tune active_block_range
use _SC_NPROCESSORS_CONF for detecting processor count
tune threads priority
use try_to_lock
add missed headers to lock
add clang to travis