Library N3657, Adding heterogeneous comparison lookup to associative containers

[associative.reqmts] Define heterogeneous lookup requirements.
[map.overview] Add new member function templates to class synopsis.
[multimap.overview] Add new member function templates to class synopsis.
[set.overview] Add new member function templates to class synopsis.
[multiset.overview] Add new member function templates to class synopsis.
[arithmetic.operations] Add typedef to void specializations.
[comparisons] Add typedef to void specializations.
[logical.operations] Add typedef to void specializations.
[bitwise.operations] Add typedef to void specializations.