Complete reimplementation of HAL DMA routines.

Complete reimplementation of HAL DMA routines.

The key changes are
* Proper support for bus-master device adapters.
* Real implementation of map registers.
* Basic support for emulating scatter/gather DMA on
  devices that don't support it in hardware.
* Support for transfers that aren't page aligned.
* Proper detection and support of EISA DMA controllers.
* Fixed prototype for HalFlushCommonBuffer.

svn path=/trunk/; revision=17470