* Smake (GNULIB_MODULES): Don't depend on memmem module, because

PSPP does not use memmem any longer.  Use
unilbrk/ulc-width-linebreaks module instead of the linebreak
module, because the latter was split up into multiple modules and
that's the one we actually need.

* automake.mk: Make install-data-hook depend on yelp-check if the
GUI is configured.

* automake.mk: Rename install-data-hook to yelp-check and mark it
phony.  This avoids an automake warning for duplicate
install-data-hook commands in doc/automake.mk and this file
(automake does not understand double-colon rules, since they are
not in POSIX).