fix docs for wxInputStream::GetC(); fixes #4461

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@56896 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/stream.h

@@ -795,6 +795,8 @@ public:
     /**
         Returns the first character in the input queue and removes it,
         blocking until it appears if necessary.
+
+        On success returns a value between 0 - 255; on end of file returns @c wxEOF.
     */
     int GetC();