instead of using linksets directly. This has two implications:
1) It is now possible to "unload" a builtin module provided it is
not busy. This is useful e.g. to disable a kernel feature as
an immediate workaround to a security problem. To re-initialize
the module, modload -f <name> is required.
2) It is possible to use builtin modules which were linked at
runtime with an external linker (dlopen + rump).
is passed, it's fixed up in kobj_subr.c), so permit MAXPATHLEN arguments.
The other commands deal strictly with module names, so leave them be.
While we're here, copyinstr()'s length parameter includes NUL-termination,
so no need to subtract 1.
