Eliminate unwanted whitespace from the man pages' XML source

Eliminate unwanted whitespace from the man pages' XML source

As demanded by the git commit hook set up by autogen.sh, this eliminates
trailing whitespace on each line, and blank lines at EOF. We might as
well do this now, since every line in these files has changed anyway.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=59805
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Ralf Habacker <ralf.habacker@freenet.de>