cocoa_common: fix a bug in window dragging state

When going in and going out of full screen the player lost information on the
movableByWindowBackground behaviour. There were some hacks in place to fix it
but they were broken with the recent native fullscreen changes in 74c15ec6.

This commit removes the problem at the root and removes the hacks. The delegate
method `isMovableByWindowBackground` seems to be called after setFrame and
setPresentationOptions so change fs state in opts before that.

Fixes #83
cocoa_common: remove pointless locking when using -fs

When using --fs `vo_cocoa_fullscreen` was called from the primary thread. This
occurred inside `vo_cocoa_config_window` which is scheduled for excution on the
primary thread with libdispatch).

All of this caused spam from NSRecursiveLock in standard output.
cocoa_common: don't use recursive locking

This was in the original change set for the threadsafety changes but I forgot
to squash it in.