Especially with other components (libavcodec, OSX stuff), the thread
list can get quite populated. Setting the thread name helps when
debugging.
Since this is not portable, we check the OS variants in waf configure.
old-configure just gets a special-case for glibc, since doing a full
check here would probably be a waste of effort.
The ipc_thread can exit any time, and will free the mp_ipc_ctx when
doing this, leaving a dangling pointer. This was somewhat handled in the
original commit by setting mpctx->ipc_ctx to NULL when the thread
exited, but that was still a race condition.
Handle it by freeing most things after joining the ipc_thread. This
means some resources will not be freed until player exit, but that
should be ok (it's an exceptional error situation).
Also, actually close the pipe FDs in mp_init_ipc() on another error
path.
