Wip

- Started implementing cocoa view. Realized that supporting open is pretty
ugly xplat. Committing to hop back on master to remove that.
Temp bashed mac-ogl.mk in Makefile.

- This branch doesn't have mechs to exclude .mm projects on non .mm targets.
Third party builds now use CMAKE --build, rather than a cooked command.
-pthread is correctly passed to gcc-compatible builds again.
Views no longer have a created but not open state.

- Supporting 2-phase construction (create, then open) is bad enough on
xlib/glx. It's a nightmare xplat. It has been disabled.
- In the future, it is likely that we'll move to having only one video object
at all, similar to sdl.
Merged from master.
Wip

Working through cocoa. Running everything on main thread is getting hard.
Thinking about building dpcs.