pinentry: fix keyboard/pointer grabbing bugs

use debian patches to get the gtk2 version to work with various tiling
window managers

Related reports:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=850708
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=851707
https://github.com/ch11ng/exwm/issues/263
https://github.com/ch11ng/exwm/issues/279