Added hold_supported attribute to IMediaStream

Ignore-this: 5aca74b9b0b25c0ef45369d9254b5472

darcs-hash:20090714161232-1e3d8-c5f3954097a7c1ac6e12729944efc9fb0ec5134b
Added AudioInputDevice and AudioOutputDevice setting types

Ignore-this: e3ffa1ea9f990ba1a021b9ebe10e13b9

darcs-hash:20090714165512-1e3d8-77396a67a3b1ee61039557423724e684a0c39225