Fix C++ examples for C++ 17 (#1723)

Signed-off-by: Darby Johnston <darbyjohnston@yahoo.com>

Author: darbyjohnston

examples/conform.cpp

@@ -96,7 +96,7 @@ int conform_timeline(
         // relink to the found path
         clip->set_media_reference(new otio::ExternalReference(
             "file://" + new_path,
-            otio::nullopt // the available range is unknown without opening the file
+            std::nullopt // the available range is unknown without opening the file
         ));
         count += 1;
     }

examples/io_perf_test.cpp

@@ -5,7 +5,6 @@
 
 #include "opentimelineio/clip.h"
 #include "opentimelineio/typeRegistry.h"
-#include "opentimelineio/any.h"
 #include "opentimelineio/serialization.h"
 #include "opentimelineio/deserialization.h"
 #include "opentimelineio/timeline.h"
@@ -133,7 +132,7 @@ main(
         print_elapsed_time("downgrade clip", begin, end);
     }
 
-    otio::any tl;
+    std::any tl;
     std::string fname = std::string(argv[1]);
 
     // read file