Bug 56923 - Make command line options consistent (single vs double dash)

Bug 56923 - Make command line options consistent (single vs double dash)

Most of xrandr's command line options follow the system of single
dashes for single character options (e.g. "-v") and double dashes for
long options ("--version").  The only exceptions are "-display" and
"-help", most likely for historical reasons.  To make the behavior
consistent across all options, the following patch adds "--display"
and "--help" as alternatives to the current inconsistency.  The man
page got updated as well, recommending double-dash variants for both
options. The old behavior is still supported, so the patch should not
break any existing usage/script.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>