Merge pull request #629 from chrox/master

GUI adaptation for smaller screens
check window stack before sending events
This should fix FC on Android with "Start with last opened file" checked
fix cannot load thrift library on Android
update luajit-launcher
fix two finger pan gestures detection
This is a stupid bug I introduced when I thought 0 evaluated to be false.
Actually in Lua only explicit `false` and `nil` are evaluated to `false`
all other values are true in logical expressions.

This should also fix #546. Probably because the touch screens in Kindle
are not as sensitive as in Kobo, this problem is not discovered early
util I play with multi-touch on a Android phone which has a sensitive
enough screen to expose this bug.