cocoa: add application icon to the Dock when run from CLI

Application icon was added to the Dock only when run inside of a bundle. That
was handled automatically by OS X using the Info.plist definition.

To add the Application icon when run as a CLI program, I used the samme
approach in the X11 code and loaded the icon as a static binary blob inside
of mpv's binary. This is the simplest approach as it avoid headackes when
relocating the binary and such.