Merge of old SVN hotplug branch into current git HEAD. Includes hotplug support for...

Merge of old SVN hotplug branch into current git HEAD. Includes hotplug support for DirectSound, WDM/KS. Both are working running in debugger but WDM/KS seems to be crashing in stand-alone build. I removed the use of struct _PaInternalInfo in hotplug/pa_front.c to reduce the size of the change. pa_win_dsound.c involved the most intricate changes due to other changes that had been made in the mean time. I've also initialized function ptrs ScanDeviceInfos, CommitDeviceInfos, DisposeDeviceInfos so this should build on all platforms.