remove direct libpng dependency on windows

Remove usage of macdeployqt in favor of CMake BundleUtilities. BundleUtilities properly finds all dependencies and adds them to the .app automatically. It also fixes rpath and install_name issues for any of the binaries or dependencies

Fix compiling on MacOS X by requiring c++11 standard. Building now requires MacOS X 10.8+ and CMake 3.9+

Add build/ directory .hgignore

Make hardware acceleration optional on MacOS X

make sure keys.csv is installed

add background to switch animation

add crocodile hat

replace jungle with opus

start gear data group implementation

fix check for static gears

Restrict girder placement in other land objects, too

disallow placing girders over airmines and moving hogs

add helper to find if a spite intersects gears

ArgParsers: Remove deprecated command-line arguments

Remember maximized state of game window

Remember maximized state of frontend window

Saucer: Restore dX after "freeze" state

Fix movement stopping when activating saucer after longjump

In hindsight my emscripten-ifdef (70d416a8f63f) is nonsense. As fpcrtl_glShaderSource() would not be defined and lead to compiling issues. So either it's 3 ifdefs (in pas2cRedo, pas2cSystem and misc.c), in order to toggle between fpcrtl_ and the native function, or alternatively have no ifdef for it at all. I'm going with none at all, which means emscripten will compile with the original (const) function prototype, being wrapped by the fpcrtl_ function, same as non-emscripten builds.

Rewrite a few CMake flag descriptions

fix shader uniform access

fix bug #750: workaround GL2 function params const-iness issues with pas2c

fix condition