zxtune-android: prev/next buttons support in notifications area.
zxtune-android: fix playlist playing crashes for old (pre-4.1) platforms.
zxtune-android: notification for i/o operations.
zxtune-android: support enumerated elements count hint for VfsDir.enumerate.
zxtune-android: support items count hint in VfsRootLocal.
zxtune-android: support items count hint in VfsRootModland.
zxtune-android: support items count hint in VfsRootZxtunes.
Fix l10n files.
zxtune-android: support approximate items count hint in VfsRootHvsc.
zxtune-android: extract and use common VfsCache code.
zxtune-android: forward navigation support for browser preview.
zxtune-android: fix playback sequence processing for last element.
Update changelog.