NetBSD 7.99.62 introduced Debug Registers interface similar to the FreeBSD one.
This interface will land NetBSD-8.0.
Introduce support for this interface in Register Context NetBSD x86_64 unconditionally as older versions of NetBSD will not be supported.
This change allows to reduce diff with other ports and remove local copy of the RegisterInfos_x86_64.h content.
NetBSD Register Context for 32-bit x86 support will be added later.
Sponsored by <The NetBSD Foundation>