Fix some memory leaks in the tests

tests/graphics/clippingbox.cpp

@@ -1230,6 +1230,7 @@ void ClippingBoxTestCaseDCBase::OneDevRegionNonRect()
                  m_dc->DeviceToLogicalXRel(clipW),
                  m_dc->DeviceToLogicalYRel(clipH), 1);
     CheckClipShape(bmpRef, 1);
+    delete memDC;
 }
 
 void ClippingBoxTestCaseDCBase::OneDevRegionAndReset()

tests/graphics/measuring.cpp

@@ -183,6 +183,7 @@ void MeasuringTextTestCase::GraphicsGetTextExtent()
     context->SetFont(font, *wxBLACK);
     double width, height, descent, externalLeading = 0.0;
     context->GetTextExtent("x", &width, &height, &descent, &externalLeading);
+    delete context;
 
     // TODO: Determine a way to make these tests more robust.
     CPPUNIT_ASSERT(width > 0.0);