format specific.
Struct emul has a e_setregs hook back, which points to emulation-specific
setregs function. es_setregs of struct execsw now only points to
optional executable-specific setup function (this is only used for
ECOFF).
since only linux compat on i386 is installed, only that LKM is actually
installed (LKMs are build for all platforms as appropriate though)
further changes to compat code would need to happen to make this usable
also for other plaforms or emulations