A yEnc encoding / decoding package without header and footer.
- Fetch the character
- Add 42
- Check for NULL, TAB(ascii 9), LF(ascii 10), CR (ascii 13) and '='
- If one of the critical chars encounters then write '=' as escape character to the output stream followed by the critical+64. (NULL -> =@, TAB --> =I, LF --> =J, CR --> =M, '=' --> =}