Remove possible double encoding from shareddir.dat
Since CTextFile already ensures shareddir.dat is written/read in UTF-8, that's
universal enough. Using CPath::{To,From}Univ() functions would require characters
outside the current system code page (or ISO-8859-1) being double-encoded in
UTF-8, rendering shareddir.dat not editable by the user.
Though it works in UTF-8 locales, fails miserably otherwise.
Regarding CPath::{To,From}Univ, it is under investigation whether these functions
are needed at all. Until then, changed back wxConvLocal to wxConvISO8859_1, the
former is definitely not a good choice.