This replaces the use of VLCEventManager to execute events on the main
thread with a libdispatch based approach, which simplifies the code and
makes it slightly more efficient.

Additionally, this deploys VLCMedia's own comparison mechanism to
determine equality instead of NSURL and removes a potential runtime
exception.

This fixes a regression on seek using the SMB2 module.

This fixes anonymous login to SMB2 servers in some scenarios.

This includes the backported patch to support DVB subtitles in mkv and
therefore fixes #602.

This updates the checkout of the mainline VLC MR to its current state.