Handle non-ASCII values in StreamPanel.

For now we just use Unicode's "Control Pictures" to represent control characters (except '\n'), and represent any other non-print value using Unicode's Replacement Character (U+FFFD). In the future we'll add better support for representing binary information.
Workaround bug with FindPage method in wxAuiNotebook.
Use a mixed ASCII and Octal display for streams that have had non-ASCII characters written to them.