Allow examples and test-suite to be built out of source tree

- top-level Makefile replicates Examples/... directory tree in
  build directory, and create symbolic links to Examples/... Makefiles
- Examples/Makefile.in sets SRCDIR to the source directory from
  a file ".srcdir" created by top-level Makefile
- test suite Makefiles set SRCDIR from autoconf-set srcdir
- lua embedded interpreters need to be passed location of run-time test
- python copies run-time scripts to build directory because of 2to3
  conversion; for test-suite, set SCRIPTDIR to location of run-time tests
- Examples/test-suite/errors/Makefile.in needs to filter out source
  directory from SWIG error messages
Build Travis CI out of source tree