Import upstream Diehard4 by obscurant

Verbatim contents of the upstream GitHub archive (Diehard4-master.zip,
commit 254ee204deebc64793123a9643c85b7d113c6c22, files dated 2019-05-21).

Imported unmodified so that every change in this fork is visible as a diff
against the original, which is what GPL-3.0 section 5(a) is asking for.
All code in this commit is obscurant's work, not mine.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

xfwm4/bottom-right-inactive.xpm

@@ -0,0 +1,9 @@
+/* XPM */
+static char * bottom_right_inactive_xpm[] = {
+"4 4 2 1",
+" 	c None",
+".	c #0D151D",
+"....",
+"....",
+"... ",
+"..  "};