resolve warnings while compiling coreX11
Merge branch 'master' of https://github.com/kivy/kivy
Merge branch 'master' of https://github.com/kivy/kivy
Merge branch 'master' of https://github.com/kivy/kivy
Make the PID available to x and add the abillety to tell the window manager that the window should be above other windows by setting the env. variable KIVY_WINDOW_ABOVE
fix comment typo
Merge pull request #1830 from jegger/x11_window_improvements

X11 window improvements