sources dialog: Don't translate a placeholder string

https://bugzilla.gnome.org/show_bug.cgi?id=726988
build: Remove autoconf checks for programs we don't use

Fixes a libtoolize warning:

    libtoolize: `AC_PROG_RANLIB' is rendered obsolete by `LT_INIT'
trivial: Also look for svgz image files

This is required for Ubuntu.
Load app-install data on Ubuntu systems