gitk: small quality of life improvements for themed Tk

These three closely related patches build on
https://lore.kernel.org/git/[email protected]
to:

1. also allow changing text wrapping preferences for users that do not use themed Tk (that is, users that have turned the "use themed widgets" preference off);
2. no longer change the background color when using themed Tk (the default) as - at least on the platforms I tried - most widgets and the main window do not change their background color anyhow, whereas some widgets do, leading to a messy looking UI where different widgets seemingly assume different background colors; and
3. use the now-available uicolor preference to draw a "sash" (grab handle) between the many panes of the main window when using themed Tk; on the platforms I tried, themed Tk was both the default and it was not rendering any sash, thus requiring users to guess where to click to resize window panes. Manually setting uicolor to a platform-dependent color (see https://www.tcl-lang.org/man/tcl/TkCmd/colors.htm#M4) in the config file works to get sashes that automatically adapt to light mode and dark mode.

Christoph Sommer (3):
gitk: fix text wrapping preferences for unthemed tk
gitk: do not set fg/bg color scheme for themed Tk
gitk: on themed tk, use uicolor to draw a sash between panes

 gitk-git/gitk | 60 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 53 insertions(+), 7 deletions(-)

base-commit: f65182a99e545d2f2bc22e6c1c2da192133b16a3
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1909%2Fsommer%2Fmaster-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1909/sommer/master-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1909

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