If a DCI string ended with a string delimiter or non-ASCII character
(e.g. a PETSCII char with no ASCII equivalent), the code generator
output the last byte as a hex value. This caused an error because it
was outputting the raw hex value, with the high bit already set, which
the assembler did not expect.
This change corrects the behavior for code generation and on-screen
display, and adds a few samples to the regression test suite.
(see issue #102)
