For both 32 and 64bit x86, have each of the exception stubs which push a
few words and branch to the common isr routine be simply 16 byte aligned
to make it easy to calculate the offset from the main isr table. This
cleans up some complexity that was actually broken for interrupts >= 0x80.
Also:
-Switch alignment directives to .balign
-Expand the x86-32 exception table to a full 256
-Remove an extraneous define
-Make sure the IDT is 8 or 16 byte aligned
-Use END_DATA and END_FUNCTION in the exception and gdt asm files
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