Fix 'make dist'
requested to merge mnowak/1769-ensure-all-necessary-files-are-included-in-the-tarball-produced-by-make-dist into master
distcheck fails because of tests, most notably because of the system test, which fails to write to the source tree because files and directories in the tarball are set read-only.
I added 1.9 tar-pax to AM_INIT_AUTOMAKE otherwise two test files won't make it to the 99 character file name limit.
Fixes #1769 (closed).