Drop the intltool dependency that was recently added, and use
upstream gettext and its its features for the same purpose.
Note that polkit currently does not install .its files (I've
sent a patch). Until that is in place, this change has the
effect of installing the untranslated policy file.
This avoids hard-coding the (potentially absolute) srcdir used at
autogen time into the build system. It's fine for an Automake build
system to use relative paths in dependencies and rely on them being
interpreted as relative to ${srcdir} even though the current working
directory is ${buildddir}, because of make's "VPATH" feature, and we
do it all the time in the handwritten parts of the build system.
In particular, this (finally) makes distcheck work.
Signed-off-by: Simon McVittie <smcv@debian.org>