Displays an error message on the screen. This function is a pointer
to an error function. You may redirect it to your own function, but
it's better to leave it unchanged.
l_int (*seal_error) ( l_int errtype, l_text str, ... );
errtype The type of error to display. These are supported in Seal 1.0:
ERR_NOTHING - No error has occured.
ERR_NONREGULAR - This is a very serious error.
ERR_INFO - This is not so serious. Just inform the
user that an error has occured.
str Contains the formatted text to display. Supports the same
formatting as the "printf()" function.
... Other strings and variables to show in text.