Fixed a small typo.
Cleaned up functional, added a few mechs.

- Added predicate functor for equal of heterogeneous types.
- Added predicate functor for equivalent.
- Optimized equivalent to use single compare for equality-comparing
types.
- Added lifted() and predicate functor.
Bashed stale include.
Updated string_ref_c for c++11's equal and lex-comp.
Added rough and untested module for iterator pairs.