Implement TypeInfo_AssociativeArray.getHash to correctly calculate hash
value for AA's.
Improve code per Andrei's suggestions.
Fix compile errors with nothrow.
Fix const-correctness of _aaGetHash.
Merge pull request #171 from quickfur/gethash_fixes

Review request: getHash candidate for TypeInfo_AssociativeArray
Merge pull request #351 from redstar/sys_un

un.d: Move public import into section protected by version (Posix)