which set the LDT and share VM space (e.g. new versions of WINE) expect
the LDT to be logically coupled to the address space. Use the new pmap_fork()
interface to copy non-shared user-set LDTs when the address space is forked.
* Call gdt_init() earlier on.
* Don't bother to check for TSS and LDT descriptors in verr_gdt().
* Nuke the sti special case for trace and breakpoint traps.
* Move some variable declarations into more appropriate locations.
Map kernel stacks only at unique addresses.
Use one TSS per process.
Add sysarch calls for modifying IOPL and the I/O permission bitmap.
Add a compacting GDT entry allocator, for TSS and LDT selectors.
Enable modifying %fs and %gs with PT_SETREGS.
Sanitize various bits of code.
