* use wxBORDER_THEME for custom controls

* compatibility with wxWdigets 2.9+: SetClippingRegion -> SetDeviceClippingRegion

compatibility with wxWdigets 2.9+: wxString::iterator::operator* aparently does not return a wxChar anymore, use cast to force conversion.

compatibility with wxWdigets 2.9+: Vector2D use *0.5 instead of /2 to prevent ambiguous conversion errors

* compatibility with wxWdigets 2.9+: Vector2D: prevent ambiguous conversion errors
* use wxBORDER_THEME for custom control

compatibility with wxWdigets 2.9+: wxString::c_str now returns an object instead of a Char*, use cast to force conversion.
TODO: This can probably be done more efficiently!

compatibility with wxWdigets 2.9+: use HandleWindowEvent instead of ProcessEvent, but this function doesn't exist in wx2.8. So, #define the former as the latter for backwards compatibility.

compatibility with wxWdigets 2.9+: Vector2D use *0.5 instead of /2 to prevent ambiguous conversion errors

compatibility with wxWdigets 2.9+: work around a bug in wx 2.9.1 (should be fixed in newer releases)

compatibility with wxWdigets 2.9+: wxString::c_str now returns an object instead of a Char*, use cast to force conversion.

Fix error introduced in r1465: in single line text box, no lines were generated (which led to a crash), or text was scaled down when this was not intended.

bufgix: with newer version of wxWidgets (2.8), image slice dialog was crashing because events were being sent before the initialization was complete.

doing that lead to conflicts in new compilers, because both boost and std contain a shared_ptr type.