rsgislib conflicts with flip

[barracuda156]

Error: Failed to activate flip: Image error: /opt/local/bin/flip is being used by the active rsgislib port.  Please deactivate this port first, or use 'port -f activate flip' to force the activation.
    while executing
"throw registry::image-error $msg"
    ("foreach" body line 49)
    invoked from within
"foreach file $imagefiles {
                incr progress_step
                _progress update $progress_step $progress_total_steps
                se..."
    invoked from within
"registry::write {
            # extract phase complete, assume 1/3 is done
            set progress_step $num_imagefiles
            foreach file $ima..."

[nilason (Nicklas Larsson)]

In 134f629803b74b69a2fbb405c6f624cfc597ebc6/macports-ports (master):

rsgislib, py-rsgislib: update to 5.1.6

rsgislib previously installed a version of the utility flip,
which conflicted with the port of the same name.
The rsgislib's version of flip has now been renamed
to rsgisflip and the conflict is now solved.

Closes: #70213