build: Bump gettext dependency to 0.18.2

This gets rid of an obsolete automake macro usage by gettext.
build: Bump automake version to 1.11

This makes sure we get silent rules support, and will allow switching
to use xz for release tarballs.
build: Switch from gzip to xz for distribution tarballs
build: Set ACLOCAL_AMFLAGS

Set the m4 include path and add request to install third-party modules
there too.
doc: Update upstream project URLs to the new site

Move the hosting to my own server now that Berlios has ceased to give
any service.
Release 1.9.1