[$] X clients and byte swapping

While there are still systems with both byte orders,
little-endian has
largely 'won' the battle at this point since the vast majority of today's
systems store data with the least-significant byte first (at the lowest
address). But when the X11 protocol was developed in the 1980s, there were
lots of systems of each byte order, so the X protocol allowed either order
and the server (display side) would swap the bytes to its byte order as
needed. Over time,
the code for swapping data in the messages, which was written in a
more-trusting era, has bit-rotted so that it is now a
largely untested attack surface that is nearly always unused. Peter
Hutterer has been doing some work to stop using that code by default, both
in upstream
X.org code and in downstream Fedora.