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

- Examples/Makefile.in rules use SRCDIR as the relative source directory

- ./config.status replicates Examples/ source directory tree in build
  directory, and copies each Makefile to build directory, prefixed with
  a header which sets SRCDIR to source directory

- Examples/test-suite/.../Makefile.in set SRCDIR from Autoconf-set srcdir

- Examples/test-suite/errors/Makefile.in needs to filter out source
  directory from SWIG error messages

- Lua: embedded interpreters are passed location of run-time test

- Python: copy run-time scripts to build directory because of 2to3
  conversion; import_packages example copies __init__.py from source
  directory; test-suite sets SCRIPTDIR to location of run-time tests

- Javascript: binding.gyp renamed to binding.gyp.in so that $srcdir
  can be substituted with SRCDIR; removed './' from require() statements
  so that NODE_PATH can be used to point Node.js to build directory