Updated TODOs.
Changed diff symbol from a block to an 'X'.

On some devices the block symbol is not implemented in the
monospace font. Therefore a different font with another width
is chosen. This messes up the whole output of the diff tool.
Added new tag to the tag identification list (TNP3xxxx).
Added more well known keys to the extended key file.
New release: 1.8.1

Updated changelog.
Increased version number.
Fixed typo in the AC file.