Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Bump shared libraries version numbers in preparation for 9.0.
This time, only libraries which ABI has been changed compared to
stable/8, are bumped.

ABI analysis done by: Gleb Kurtsou
Approved by: re (kensmith)

Import the librtld_db library. This is needed by userland DTrace.
This is not yet enabled in the build because I also need to import a new
version of libproc.

Sponsored by: The FreeBSD Foundation