tkdiff Code

Resolving small inconsistencies in startup behavior and messages
- add/align extra failure msgs regarding insufficeint items to compare
- reduce confusion (int/ext-ernal) about when newDiffDialog appears
- simpler solution to earlier (-r103) fix (avoiding 'string cat' use)
- increase 'package requires tk' to minimum version of 8.5
- add missing 'update-display' call if startup yeilds zero diffs

Use join instead of string cat, to preserve compatibility with wish 8.5

Revise Git detection and reset multifile choice after a new diff

Reworked contrib'd "Git multi-file" feature to fit within an overall internal
redesign allowing for other sources of multiple files (dir-to-dir, other SCMs),
while also addressing its original integration missteps of existing features
it mangled (notably edit, report output, and a lack of online help info).

Repair condition chk for Split activation when only 1 hunk exists

Provide Split/Combine diff hunk feature

"tag_copy_by_TkSVN"

"tag_copy_by_TkSVN"

"tags_directory_path_by_TkSVN"

"Removed_using_TkSVN"