Added support for -u username:group format, which overrides the -g option.
Added support for -u username:group format, which overrides the -g option.

Documentation updated to reflect new feature.

Linux perl is silent and does not do anything when you try to set the
gid of a file to a non-existant group (even by direct id), so a warn
about invalid group being set changed to a die.

princeofdarkness76/sial.org-scripts,thrig/scripts,thrig/scripts,thrig/scripts,princeofdarkness76/sial.org-scripts,thrig/scripts,princeofdarkness76/sial.org-scripts,thrig/scripts,thrig/scripts,princeofdarkness76/sial.org-scripts,princeofdarkness76/sial.org-scripts