The CD-ROM IOCTL direct pass through code now does sanity check on the requested data size before passing the command - fixes crashes with some DMA-only host DVD drives;
The network poller is now in its own thread;
The hack is back in the emulation of the National Semiconductors PC87306 Super I/O Chip - it's the only way right now to have serial working on that board;
Fixed a part of the code that was still using NukedOPL even when OPL 3 was set to DOSBox OPL;
Applied all mainline PCem commits.
