#238 Allow custom ttk states

[Thomas Perschak]

Currently the widgets states are limited to "focus", "disabled", "pressed", "readonly" ... and some free states "user1", "user2" and "user3" (see ttkState.c const stateNames);
In order to build custom widgets I propose extending the state list during runtime operation, such that states like "warning" and "error" could be defined.

This feature request is raised because of the following:
http://sourceforge.net/tracker/?func=detail&aid=3439581&group_id=12997&atid=362997
http://groups.google.com/group/comp.lang.tcl/browse_thread/thread/f397b04c019aed9e?hl=en

thx