* Fix grid select box update bug on context menu.
* Fix via size and track width select box update bugs.
* Fix layer pair indicator button update bug.
* Fix auto track width tool bar control enable bug.
* Fix via size and track width select status bug in context menu.
* Fix layer select box and layer control widget select bug when current
layer is removed.
* Add virtual function to notify objects derived from EDA_DRAW_FRAME that
the units setting has changed.
* Coding policy class naming fixes.
* Rename all member variables and methods that reference the cross hair
code in draw panel object from cursor to cross hair to eliminate confusion
between the two concepts.
* Rename cursor capture call backs in draw panel object to improve code
readability.
* Create helper class for turning off the cross hair while drawing.
* Remove redundant block clear code.
* Remove redundant mouse capture call back reset code when end capture
call back is called.
* Remove unused function definitions in base draw frame object.
* Lots of minor coding policy and doxygen comment fixes.
jean-pierre charras
Wayne Stambaugh
Dick Hollenbeck
charras