ci scripts in pspp source tree

[Friedrich Beckmann]

I have worked on the continuous integration on github/travis and
on the dedicated pspp build server with buildbot. Up to now I have
kept the ci scripts in a dedicated branch on github but now
I would like to merge this into savannah master. The change
will introduce 

  * a new directory „ci“ which contains build scripts
  * a new file .travis.yml (script instructs)
  * a modification of the Makefile.am to ignore the ci
    files in the git-distribution check

The changes are here:

https://github.com/fredowski/pspp/compare/travis

Do you mind the merge?

The current builds are:

a) from the current git

   on buildbot http://caeis.etech.fh-augsburg.de:8010/#/builders
    -> debian-sid-i386
    -> debian-sid-amd64
    -> debian-buster-amd64
   on travis
    -> https://travis-ci.org/github/fredowski/osxbundler (MacOS)
    -> https://travis-ci.org/github/fredowski/pspp (Ubuntu bionic)

b) from Bens nightly build distribution package or stable release

   on buildbot
    -> opensuse
   on travis 
    -> https://travis-ci.org/github/fredowski/homebrew-pspp (MacOS)

All linux builds and probably also a future windows cross build can
be done on the buildbot server but the MacOS builds can only be
done on travis.