the last parameter of XChangeProperty is the number of elements.. and when the element format is 32.. the element is "long" so we have 5 long elements here.

Yes this seems confusing as on mac+linux Long is either 32 or 64bits depending on the architecture, but this is how the X11 protocol is defined. Thus 5 is the correct value for the nelts here.  Not 5 or 10 depending on the architecture.

More info on the confusion https://bugs.freedesktop.org/show_bug.cgi?id=16802

docs/README-hg.md

@@ -0,0 +1,25 @@
+Mercurial
+=========
+
+The latest development version of SDL is available via Mercurial.
+Mercurial allows you to get up-to-the-minute fixes and enhancements;
+as a developer works on a source tree, you can use "hg" to mirror that
+source tree instead of waiting for an official release. Please look
+at the Mercurial website ( http://mercurial.selenic.com/ ) for more
+information on using hg, where you can also download software for
+Mac OS X, Windows, and Unix systems.
+
+    hg clone http://hg.libsdl.org/SDL
+
+If you are building SDL with an IDE, you will need to copy the file
+include/SDL_config.h.default to include/SDL_config.h before building.
+
+If you are building SDL via configure, you will need to run autogen.sh
+before running configure.
+
+There is a web interface to the subversion repository at:
+	http://hg.libsdl.org/SDL/
+
+There is an RSS feed available at that URL, for those that want to
+track commits in real time.
+