Allow to read back the rectangle of a tab container
Fix for issue #16: correctly compute the mouse deadzone when dragging a tab to avoid skipping some of them.
Fixed signed/unsigned compilation warning by making wxAuiManager::GetActivePane() return value type consistent with other GetActive...() API that can return wxNOT_FOUND.
Merge pull request #17 from lpoujoulat/wxAuiExperimentalFixes

Fix for issue #16