Revert "SWIG: ensure Octave configuration header is always included"

- This wasn't the problem ...
- Reverts commit d89f32914aa20b68c9c28c7e78cc4c993447bd93.
SWIG: make compatible with Octave version checking in SWIG >= 2.0.12
SWIG: work around Octave's broken inclusion of <config.h> in its public headers

- This means that /path/to/octave/include/octave-x.x.x/octave has to be
  the very first -I on the command line, to override the LALSuite <config.h>
- See Octave bug: http://savannah.gnu.org/bugs/?41027