Change gdt to segment so that it can be reused for idtS and make sense.
Start idt
Revert "Change gdt to segment so that it can be reused for idtS and make sense."

This reverts commit dcdcaae5bb626b77cc92e01888bcc413066ac614.

They are a little too different.

Conflicts:
	sys/i686/i686_cpu.c
	sys/i686/i686_cpu.h