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)

Add a64l(), l64a(), and l64a_r() XSI extentions. These functions convert
between a 32-bit integer and a radix-64 ASCII string. The l64a_r() function
is a NetBSD addition.

PR: 51209 (based on submission, but very different)
Reviewed by: bde, ru