Further docs clarification

Author: cwoffenden

site/source/docs/api_reference/html5.h.rst

@@ -927,9 +927,9 @@ Defines
     Emscripten `orientationchange <https://w3c.github.io/screen-orientation/>`_ event.
 
 
-.. c:macro:: EMSCRIPTEN_ORIENTATION_UNSUPPORTED
+.. c:macro:: EMSCRIPTEN_ORIENTATION_UNKNOWN
 
-  The orientation API is not supported.
+  Either the orientation API is not supported or the orientation type is not known.
 
 .. c:macro:: EMSCRIPTEN_ORIENTATION_PORTRAIT_PRIMARY
 
@@ -958,7 +958,7 @@ Struct
 
   .. c:member:: int orientationIndex
 
-    One of the :c:type:`EM_ORIENTATION_PORTRAIT_xxx <EMSCRIPTEN_ORIENTATION_PORTRAIT_PRIMARY>` fields, or -1 if unknown.
+    One of the :c:type:`EM_ORIENTATION_PORTRAIT_xxx <EMSCRIPTEN_ORIENTATION_PORTRAIT_PRIMARY>` fields, or :c:type:`EMSCRIPTEN_ORIENTATION_UNKNOWN` if unknown.
 
   .. c:member:: int orientationAngle