Linux does not handle the resize command with wide-character extended
table UTF-8. The solution did not work for W7-32bit. This is a
compromise, attempting first the preferred, previous solution and
falling back to the secondary solution.
(cherry picked from commit 6106210c87)
This forces the compiler class specific features rather than borrowing
from the base class's std::string. In some cases prior to this,
wxString( std::string ) was being called rather than UTF8::operator
wxString() leading to garbled wxStrings.
Added function UTF8::wx_str() which is of great convenience also.
Implicit conversions still work as before, and hopefully more reliably.