Fix to compile warnings.

* discarded-qualifiers warnings.
* Function definitions, the .h doesn't match the .c.
* Added some include to ensure the .c has function definition.

cde/lib/DtHelp/Graphics.c

@@ -2748,7 +2748,7 @@ void _DtGrRegisterConverter(
  *****************************************************************************/
 int _DtGrOpenFile(
     _DtGrStream *stream,
-    const char  *path)
+    char  *path)
 {
     char *fname = NULL;