distribute: add hash-name-regex option

This is to support the common "write to temp file then rename" idiom. In our
case this causes us to create a linkfile during the rename in (N-1)/N cases,
with a significant impact on performance e.g. for UFO which uses this idiom.
This patch allows the user to specify up to two regular expressions that
separate the permanent and transient parts of a temp-file name:

    rsync-hash-regex reimplements the existing RSYNC_FRIENDLY_NAME
    pattern where the temporary name for EXAMPLE is .EXAMPLE.suffix

    extra-hash-regex can be used for a second pattern, active concurrently,
    and can include alternatives via the POSIX extended-regex syntax

Change-Id: Ic1a6ed19324bc31fefe91ee34b8478877a9c5d2c
BUG: 912564
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/4116
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>