created "playground" scenario
Merge branch 'master' of https://github.com/idupree/Lasercake
fix GCC 4.6
made 'playground' the default scenario

the old default scenario is now called 'empty_box'
limited the acceleration of "jump"

so that you can jump a little without having to
   wait a while to come down, or slow your descent
   without immediately popping upwards again.
I also renamed it to "jump/fly" to be more accurate.
neatened up conveyor code
Made conveyor-corners more practical

Now, conveyors also cause tiles to stay on the
   conveyor axis instead of sliding off to the side.
This behavior is actively beyond what would happen due to
   mere friction of the type that already exists in
   the tile-physics code... not that that friction
   has a pricipled reason to be as it is.
added dir param to conveyor_belt()
Added starting refinery/conveyors to 'playground'
Made the robot start in a nicer place in 'playground'
hackily fixed underflow issue
"THROW_RUBBLE" is now a little push forwards

instead of a big throw back through yourself,
   for which you pretty much can't see what's
   going on.
halved starting metal

so that you can gather metal / deconstruct objects
   right away
Fix -m32

( -DCMAKE_C_FLAGS=-m32 -DCMAKE_CXX_FLAGS=-m32 )
Fix mingw build
update DEVELOPER_README
partially fix USE_BOOST_CXX11_LIBS with GCC 4.6

We don't actually need it to work, and I couldn't get other
parts of the code to compile, but I might as well commit this.
add unused kill-simulator-thread-at-exit code for future reference
add CMake toolchain files for mingw-w64
Add trickily-missing Boost header files.