devel/xdg-utils: Update to 1.2.1

Use textproc/xmlto instead of textproc/minixmlto as the latter produces
errors with <uri> tags.

Adopt/adapt patches for xdg-su from OpenMandriva. [1]

Don't apply subsitutions to .orig files in the post-patch target.

Pet portclippy(1).

Obtained from: https://github.com/OpenMandrivaAssociation/xdg-utils/blob/rolling/xdg-utils-find-kdesu6.patch [1]

		https://github.com/OpenMandrivaAssociation/xdg-utils/blob/rolling/xdg-utils-1.2.1-lxqt-unquote.patch [1]