Fix invalid test to check if the video mode change has no effect.
The layers are not rendered with a ratio that would make their content smaller than the screen.
Fix the position of the label in the buttons with no icons.

The label appeared with twice the margin on the left. Now the margin is applied
to the label only if the icon has a non zero width.
Move the render work into a separate thread.
Do not render if there is nothing to do.
Fix incorrect return value of end_render().
Add a mutex on the stop condition of the render loop.
Add a key code to handle the "back" button of the keyboard.

This commit fixes the way the result of SDL_GetKeyboardState was handled. The
function returns scan codes but we used to process them as key codes.
The buttons and the checkboxes react to the finger events.
Merge branch 'master' of github.com:j-jorge/bear into android-render-thread

Conflicts:
	bear-engine/core/src/visual/code/gl_screen.cpp
Displays and actives a resizeable border around the configuration frame.
Merge pull request #2 from seb777/master

Displays and actives a resizeable border around the configuration frame.
Moving from GPL2 to GPL3.
Merge branch 'master' of github.com:j-jorge/bear
Clean up and bug fixes in the slopes.

Remove the threshold used to cancel the move of an item.

Do not give any force when the movement is lower than the friction.
Code clean up and little hack in the slopes.

The items put on the slopes tend to gain speed due to the collision repair
event if they don't move. If their movement is lower than one unit, we do
not apply the collision repair.
Add a pretty string formatter for boolean expressions.

The function builds a human readable string out of the content of the
expression. The main purpose is to ease the debugging of these functions.
The mouse buttons are ignored on Android builds.

The goal is to avoid being notified of both the finger and mouse events when the
user touches the screen.
Code clean up.

Moves the process of triggering the toggle in a separate function.
System toggles reacts to the fingers on pressure only.