Linux/Mips emulation is progressing quickly. To fix the system call
   shift, I added a -4000 offset in sys/arch/mips/mips/linux_syscall.c, but
   it would be nice to have a nicer implementation: I have to completely
   duplicate sys/arch/mips/mips/syscall.c just to have a -4000 on two
   lines. 
   
   Adding a new field to struct emul would a cleaner way of dealing with
   this. Something like e_sysshift which would be zero for everyone, and
   4000 for Linux/Mips. 


couldn't you:

	- have a runtime test in mips/syscall.c ?

	- or, have mips/linux_syscall.c #include mips/syscall.c, but
	#define some magic first?  kinda like kern/exec_elf64.c?