Converts the specified string `s' from `type' to `newtype', storing at most `size' bytes into the output
`buf'. The type parameters can use the value U_CURRENT as a shortcut to represent the currently selected
encoding format. Example:
char temp_string[256];
do_uconvert(input_string, U_CURRENT, temp_string, U_ASCII, 256);
Note that, even for empty strings, your destination string must have at least enough bytes to store the
terminating null character of the string, and your parameter `size' must reflect this. Otherwise, the
debug version of Allegro will abort at an assertion, and the release version of Allegro will overrun the
destination buffer.