`forge()` does not write the modified message to `out`

[Pavel Kirienko]

The docs state that out is populated with the modified message but it is not:

crchack/forge.h

Line 31 in 7902c05

  * Output buffer `out` receives a modified message with the desired checksum. 

The out argument is currently unused. I might be being overly pedantic since the docs are admitted to be incorrect, but still.

Thank you for this tool, by the way, it is quite helpful!