Bring the x86-64 architecture code uptodate for 2.5.73.

One problem is that CONFIG_IDE_TASKFILE corrupts file systems on AMD 8111. It
may be worth to disable it in the configuration.

 - Disable 32bit vsyscalls for now until all bugs can be fixed
 - Fix warnings
 - Fix NULL pointer reference in 32bit ptrace
 - Timing fixes from John Stultz
 - Sync show_stack prototype
 - Sync nmi and floppy.h code (Mikael P.)
 - Set proper defines for AGP
 - Make Simics work again
 - Scale unit in 32bit sysinfo (originally from ppc64)