Previously, using m_option_type_alias required that the alias have the
full name of the option value. This is limited if you are reusing the
same opts struct in different sub options. Fix this by add an additional
field to m_option to signal whether or not prefixes should be taken into
account for the alias option. Instead of blindly using whatever is
stored in opt->priv as the name, we can construct the desired option
name for either case (using the prefix or not).
Dudemanguy
26029cfbb0