ctf: Import ctf.h from OpenBSD

Use it instead of the existing ctf.h from OpenSolaris. This makes it
easier to use CTF in the core kernel, and to extend the CTF format to
support wider type IDs.

The imported ctf.h is modified to depend only on _types.h, and also to
provide macros which use the "parent" bit of a type ID to refer to types
in a parent CTF container.

No functional change intended.

Reviewed by: Domagoj Stolfa, emaste
MFC after: 1 month
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D34358