OIIO: added support for OIIO 1.x

OIIO 2.x uses std::unique_ptr while 1.x uses raw pointers. Olive can now handle
both, manually destroying the raw pointers when necessary if running on OIIO
1.x.

app/codec/oiio/oiiodecoder.h

@@ -46,7 +46,11 @@ public:
   virtual bool SupportsVideo() override;
 
 private:
+#if OIIO_VERSION < 10903
+  OIIO::ImageInput* image_;
+#else
   std::unique_ptr<OIIO::ImageInput> image_;
+#endif
 
   int width_;