segmentation once more...

[Jens Nerche]

A second look on GDT handling raises another question:
in emulat_lgdt are guest_gdt_info.[limit|base] changed, 
but (in nexus) is mon_gdt_info loaded. Seems that lgdt
in guest doesn't change any relevant table. (??)
(But why I can crash vm with lgdt?)

jens