CPP13 — UTF-8 and IDL character types in C++

implementing support for wchar/wstring I ran into some potential
problems with the UTF-8 encoding for the IDL 'char' type.

Lets suppose we have a C++ server with a native single-byte code set
like ISO 8859-1.
The Code Set Conversion specification states that UTF-8 is the fallback
code set for 'char'.
-> a client could decide to send characters in UTF-8 encoding.

What happens on the server side with UTF-8 encoded characters that use
more than 1 byte and thus don't fit into the single byte character as
specified by the C++ mapping for IDL type 'char'?