Log Message:
Update to 2.3.1

Disable install of documentation.

Changelog:
17.09.2011 - 2.3.1
Fixed minor issue in mode table builder.

16.09.2011 - 2.3.1
Fixed minor issue in interpreter.

11.09.2011 - 2.3.0
Fixed minor issue in code generator.

09.09.2011 - 2.3.0
Fixed medium issue in mode checker.

06.09.2011 - 2.3.0
Fixed minor issue in the scanner.

02.09.2011 - 2.3.0
24.08.2011 - 2.3.0
Fixed minor issues in mode checker.

18.07.2011 - 2.3.0
Alpha: non-local environs.

14.07.2011 - 2.3.0
Alpha: ghost elements for empty rows.

09.07.2011 - 2.3.0
New self-consistency criterion for the mode table builder.