It seems to be possible for a user to back out of a screen before
receiving the "dialog completed" callback on Android, in which case
things pointed to by the callback might be gone.
In this case, it's better to simply not call the callback, rather than
crashing.
This is accomplished by assigning "Tokens" to screens that cause
requests, and in ~Screen, invalidate any pending requests belonging to
that token.
Instead of being a popup. This should make it easier to make sure things
work normally, and avoids some of the strange overrides of PopupScreen it
previously had.
* Move and rename file_util/fd_util to Common/File/FileUtil and DirListing
Let's also move net while we're at it.
Move the ZIM/PNG loaders over to Common.
Move the UI framework into Common
iOS buildfix
* Buildfix
* Buildfixes
* Apple buildfix
* This typo again..
* UWP buildfix
* Fix build of PPSSPPQt, such as it is (it's not in good condition...)
* Guess what? Another buildfix.
