x86_64 core updates.

 - Make it compile again (switch_to macros etc., add dummy suspend.h)
 - reenable strength reduce optimization
 - Fix ramdisk (patch from Mikael Pettersson)
 - Some merges from i386
 - Reimplement lazy iobitmap allocation.  I reimplemented it based
   on bcrl's idea.
 - Fix IPC 32bit emulation to actually work and move into own file
 - New fixed mtrr.c from DaveJ ported from 2.4 and reenable it.
 - Move tlbstate into PDA.
 - Add some changes that got lost during the last merge.
 - new memset that seems to actually work.
 - Align signal handler stack frames to 16 bytes.
 - Some more minor bugfixes.