Fix "ghost stacks" created when a player clicks an item on the ground:
since the object is not immediately removed, any other code may still
think an object is there, therefore leading to item duplication. This code
therefore sets the itemstring to '' after the object is picked up to avoid
such issues
Fix double sending of chat messages
Merge remote-tracking branch 'minetest/master'
Set -std=c++0x in CMakeLists.txt

Conflicts:
	src/cmake_config.h.in
Fix merge mistake when rebasing for PR #1169
Merge remote-tracking branch 'minetest/master'

Conflicts:
	src/environment.cpp
Fix crash/error on main menu

Easy to reproduce, start minetest in such a way that the Client tab
opens first, with the username box already filled in. (in other words,
you've played it before, and used Client last time). The password box
will have focus. Press cursor up. Lua 'crash'.
fix ele if
Merge remote-tracking branch 'upstream/master' into con