#26 Datafile function no longer reports illegal characters

[Kevin Rogers]

The MISHAP generated when an encoding error occurs is
missing important information about the character
that cannot be encoded.

MillScript 10.0.0 reported the unmappable characters
in a datafile, if they could not be written in the
current output encoding. MillScript 10.1.2 has
reverted to awful Java "Input length = 1" error
message. This needs to be corrected globally for all
renderers.