[FREELDR]

[FREELDR]
- Use 'DiskReadBufferSize' instead of hardcoded values in hwdisk.c
- Transform reactos_arc_disk_info into a ARC_DISK_SIGNATURE_EX structure, so that its conversion into a ARC list in winldr.c becomes a bit simpler.
- In winldr.c:
  * In case we fail to either open the SYSTEM hive or scan it, bail out with an error message, instead of trying to continue loading ROS.
  * Fix an old comment related to ACPI;
- In memory.c/h: Do some cleanup (in particular, just use the MachXXX macros instead of also defining functions with the same names as the macros, and which just redirect into the virtual table).

svn path=/trunk/; revision=73606