Option synonims

[Paolo Redælli]

You may have noted that I used "--all-clients" instead of "-all_clients" 
which is documented in short help message.

Do we know that we may use "--" instead of "-" and "-" instead of "_" in 
options?

I.e.: -no_warning --no_warning -no-warning and --no-warning are all 
synonims for the same option.

Shall I make it a little more known, perhaps changing the help message?