Print the error message corresponding to an error number.
@param stream The stream to write to.
@param errnum The error number.
@param messageNULL, or a pointer to a message string which will
be prepend to the error message, separated by a colon and space.
Print the error message corresponding to an error number.
@param stream The stream to write to. @param errnum The error number. @param message NULL, or a pointer to a message string which will be prepend to the error message, separated by a colon and space.