Log Message:
kdiff3: update to 1.9.3

(Upstream change log incomplete in summarized form, highlights for the
1.9 bump follow.)

Version 1.9 - 2021-
===========================
*Rewrite of SourceData::FileData::preprocess now only loops through file \ 
contents once.
*Major rework of event handling
  -Move away from event filters where feasible, drop code for events now handled \ 
by qt.
  -decentralize handlers
*take advantage of Qt and boost signal/slot pattern to avoid needless nullptr checks.
  -decentralize cut/paste handling
*Introduce LineRef wrapper class
*Add enum types and use existing ones.
  -improves readability of code.
*split out doDirectoryCompare from improveFilenames
  -Principle of least surprise
*Stop mis-using c style [] pointer access there is no documented reason to \ 
assume QVector<T> has a
  c-style memory layout. Much less that this will remain so.

Not even going to try to list everything here.

See git history for complete log.