solved NetworkMonitor build with MinGW

INetworkListManagerEvents works only for MS Vista and above
MinGW: fix crash on close
Fix .travis.yml
Fix build on Linux
Fix build on Mac
TreeWidget: avoid unintentional drags

Respect QApp::startDragDistance & startDragTime
TitleBar: expand when hovered
TitleBar: cleanup unused code
TreeWidget: remove dysfunctional parent item hilite
Fix alert for "visible" private messages the when window is inactive
Turn off the horizontal scrollbar for the user list view
TitleBar: the extra top margin is only needed on Mac
TextBrowser: move cursor to the bottom when changing the document
TitleBar: collapse when the buffer changes
Fix restoring of the current buffer when it's a network buffer
Prepare ZncPlugin for playback "lowlight"
TextDocument: fix playback visualization
Update ZncManager
Tweak the unseen indicator
Disable broken playback highlight for now