sdl: Added a patch to accept all framebuffer modes
opendingux: Added the "gsensor" script to start/stop the gravity sensor
opendingux: Disable the gravity sensor when the frontend menu respawns

The gravity sensor is enabled on demand by OPKs. When the menu respawns
it is safe to assume that it is not needed anymore.
opendingux: Added an udev rule to create the /dev/input/gsensor symlink

As the mxc6225 module is loaded on demand, we never know which node
corresponds to the gravity sensor. Having udev make a symlink ensures
that we always use the correct node.
apitrace: Add missing dependency towards host-python
sdl: Enhance the triple-buffering patch

Previously, it was not possible to change the resolution or pixel
mode with a new call of SDL_SetVideoMode, a black screen was displayed
instead.

The patch was also more complex than needed, with the use of two mutexes
instead of only one.

Finally, a race could occur if FB_FlipHWSurface was called before the
thread was started; this new version of the patch also fixes this.
opendingux: gsensor: More efficient use of "grep"

We can check the exit code instead of the output string.