Remove the now-unused DYND_PP_OUTER preprocessor metaprogram
Remove the unused DYND_PP_JOIN_OUTER preprocessor metaprogram

The OUTER algorithms were much larger than the others in gen.hpp,
we have replaced their usage with C++11 variadic templates. By
removing them, the preprocessor has a bit less text to process.
Merge pull request #174 from mwiebe/pp_simplify

Remove the OUTER preprocessor macro metaprograms