Updated Czech translation
configure: Use autoconf AC_GNU_SOURCE macro
Use autoconf macros for strptime detection
Update gnulib internal copy: compile warnings fixes
Do not depend on intltool: Use upstream gettext instead

gettext recently added GtkBuilder format support, so no need
on depend on intltool anymore
po/*.po: Update translations
Updated POTFILES.in

Yeah, you kinda need the tags for translators to be able to translate them...
The AC_FUNC_MKTIME macro is obsolescent.

New programs should use Gnulib's mktime module.
configure.ac: Remove unnneded checks

They are pretty standard and ee do not provide an alternative anyway
autogen.sh: Abort if autoreconf fails
Add gnulib stuff in tree