Merge pull request #127 from alexmarsev/highdpi

Higher DPI
Don't revert window title when changing media
Playlist: ability to add all media files in folder
Playlist: treat one item as always hovered
Correctly account for panels docked at the top

There was 2px error previously
Playlist: fix layout calculation on resize

When vertical scrollbar was (dis)appearing, the layout was wrong
Mouse: send wheel messages to hovered windows
VolumeCtrl: make mouse wheel consistent

Wheel up - volume up, wheel down - volume down.
And use the same steps as volume control command.
PlayerListCtrl: internal timer hack
Don't auto-hide controls that have mouse capture
Mouse: better double-click processing
Mouse: move popup menu notification to MpcEvent
VideoRenderers: blit correctly to negative windows

Needed for showing/auto-hiding docked panels and main menu without
rescaling the video
XySubPic: clip before memcpy
Update Changelog.txt