Fixed a IMGUI_API->inline case (#657, #349)

imgui.h

@@ -791,7 +791,7 @@ struct ImGuiIO
     // Functions
     IMGUI_API void AddInputCharacter(ImWchar c);                        // Helper to add a new character into InputCharacters[]
     IMGUI_API void AddInputCharactersUTF8(const char* utf8_chars);      // Helper to add new characters into InputCharacters[] from an UTF-8 string
-    IMGUI_API void ClearInputCharacters() { InputCharacters[0] = 0; }   // Helper to clear the text input buffer
+    inline void    ClearInputCharacters() { InputCharacters[0] = 0; }   // Helper to clear the text input buffer
 
     //------------------------------------------------------------------
     // Output - Retrieve after calling NewFrame(), you can use them to discard inputs or hide them from the rest of your application