Changes in version 0.14:

Ocrad is now able to read ppm (color) files.

The internal representation is now a 256-level greymap instead of a
bitmap.

Automatic and adaptive binarization has been added, allowing the removal
of colored backgrounds.

A new option `--crop' has been added.

Two new chapters `Image Format Conversion' and `Algorithm' have been
added to the texinfo file.

Target `check' has been added to Makefile.

Some fixes and small improvements have been made.
