[within][winding] Add more robust calculation of sides in winding strategy.

This commit fixes the ticket https://svn.boost.org/trac/boost/ticket/9628.
The side is calculated always WRT the vertical segment if the p<1> is "equal" to one of the segment endpoint's <1>.
For more information see the comment in the code.
[test][within] Comment out, mistakenly not commented out line
[strategies][winding] Replace Points creation using copy-ctors with default-ctors + set<>()

Also add some comments about what's going on in the code.
Merge pull request #95 from awulkiew/feature/point_in_geometry

Fix for within() - ticket https://svn.boost.org/trac/boost/ticket/9628