The patch in summary is touching both Makefile.in and Makefile.am, probably to avoid autotools rebuild.
This treatment is usually reserved for a few selected system packages that cannot have their autotool scripts rebuilt.
This _could_ cause maintainermode-driven rebuild (see http://blog.flameeyes.eu/articles/2008/06/13/maintaner-mode ), which is something we should be avoiding as much as possible.
Please just patch Makefile.am and/or configure.in/.ac and rebuild autotools, unless you have very good reasons not to.
It is doing so because several different directories exist, some only with Makefile.in and some with Makefile.am. Guess you didn't think about that edge case. :-)
Sincerely, I didn't expect it at all :) But I remember now looking at wml before, and it gave me enough creeps without knowing it deeply :P sorry for the noise