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This converts the KWSys license to a pure 3-clause OSI-approved BSD
License.  We drop the previous license clause requiring modified
versions to be plainly marked.  We also update the KWSys copyright to
cover the full development time range.

ENH: Added KWSys try-compiles KWSYS_STL_HAS_ITERATOR_TRAITS, KWSYS_STL_HAS_ITERATOR_CATEGORY, KWSYS_STL_HAS___ITERATOR_CATEGORY, and KWSYS_STL_HAS_ALLOCATOR_NONTEMPLATE to get the hash table to compile on old HP and Sun compilers.

COMP: Replacing _Select1st with a specialized hash_select1st that avoids requiring the stl pair to have first_type defined.  The old HP STL does not define first_type and second_type in its pair.

COMP: Remove friend templates and always use template friends (possibly with <>).  Needed to work-around Sun CC bug.

ENH: Adding SGI hash_map and hash_set implementation ported from STL to KWSys.  This also adds try-compiles for KWSYS_STL_HAS_ALLOCATOR_REBIND, KWSYS_CXX_HAS_FULL_SPECIALIZATION, KWSYS_CXX_HAS_MEMBER_TEMPLATES, and KWSYS_CXX_HAS_NULL_TEMPLATE_ARGS.