Use Posix regex(3) within src/bucoord/commands.c

Use Posix regex(3) within src/bucoord/commands.c

Normally pattern matching against volume names is done on the server, but
if this fails, the client (src/bucoord/commands.c) is doing this.
This program had no code to use regex(3) when HAVE_POSIX_REGEX is defined.
This patch adds calls to regex(3) if HAVE_POSIX_REGEX is defined.
For systems without POSIX regex there were two (slightly different)
implementations in src/bucoord/regex.c and src/util/regex.c. The newer
version src/bucoord/regex.c has been modified and moved to src/util/regex.c.
Some header files and Makefiles have been removed/updated to work with this
setup.

Reviewed-on: http://gerrit.openafs.org/http://gerrit.openafs.org/99
Tested-by: Russ Allbery <rra@stanford.edu>
Reviewed-by: Russ Allbery <rra@stanford.edu>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>