tkdiff Code

Enhanced features and preference display/edit for flexibility/speed
* Multiple Diff suppression features now supported
- Can request suppression of diffs involving only empty lines
- Additionally, may also suppress diffs of RegExp-matched lines
- both features are retained/manipulated as user preferences and
may also be specified from the command line
- suppresion modes work REGARDLESS of the Diff engine in use
* New prefs added, exposing more existing configuration settings
- A preferred merge choice default (ie. initial choice of side)
provided as both a commandline and preferences setting
- Colors representing diff region categories in the map and
the interim CDR color used during Split/Combine interaction
* A builtin interactive color selector for tuning above colors
* builtin (default) editor now positions to current CDR line
* avoids RE-highlighting unless pertinent values were changed
* (internal upgrade of combobox widget from V2.2.2 to V2.3)
* Another extensive update to the online help to explain it all

Provided a catchall commandline error msg (should never occur) to avoid crashing
Inline-diff computation now runs faster (implementation tuning)

Bug #55 "tkdiff -conflict FILE" invocation doesn't work

Explain how to use it on Windows and MacOS.

"tag_copy_by_TkSVN"

Merge from r116

Repaired missing Wheel scrolling over merge-preview Info window

(Last) Minor behavioral refinements addressed
- Button-2 jump scrolling now works over the Map when zero diffs exist
- Misleading dead code removed related to map scrolling
- Help info on cmdline quoting rules refined

ipadx -1 on the merge window buttons makes it so that they get big enough for the whole text string to fit. This may have only been a problem on Windows and Mac.

OK I think I'm done now.

Work on Aqua UI some more. Reworked the Merge window a little so that the frames are properly configurable.