Fixes to build on openSUSE/Packman. (#67)

- Support different BINDIR, INCLUDEDIR and LIBDIR on install
- Take right python dir on x86_64 arch
- Fix build against Boost >= 1.58
- Make it possible to build libIfcGeom shared to reduce size of dependent binaries
- Fix INSTALL_RPATH
- Fix some more compiler warnings

src/ifcwrap/IfcGeomWrapper.i

@@ -387,6 +387,7 @@ struct ShapeRTTI : public boost::static_visitor<PyObject*>
 				throw IfcParse::IfcException("Invalid additional representation specified");
 			}
 		}
+		return boost::variant<IfcGeom::Element<double>*, IfcGeom::Representation::Representation*>();
 	}
 %}