doc:  link/caps fixes for 9.4 release notes

Report by Tomonari Katsumata
Silence a couple of spurious valgrind warnings in inval.c.

Define padding bytes in SharedInvalidationMessage structs to be
defined. Otherwise the sinvaladt.c ringbuffer, which is accessed by
multiple processes, will cause spurious valgrind warnings about
undefined memory being used. That's because valgrind remembers the
undefined bytes from the last local process's store, not realizing
that another process has written since, filling the previously
uninitialized bytes.
Replaced UUID-OSSP with BSD/Linux implementations
Fixed NetBSD build
Filter extension linking to pick libuuid only

Also removed libmd from AC_SEARCH_LIBS.
Fixed v3 and v5 according to the RFC errata

http://www.rfc-editor.org/errata_search.php?rfc=4122
Fixed Linux variant according to the RFC errata

http://www.rfc-editor.org/errata_search.php?rfc=4122
Added regression tests
Improved comments
Removed now useless UUID_LIBS from Makefile
Updated configure
Removed reference to uuid-freebsd