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/GraphicsP.h

@@ -72,7 +72,7 @@ typedef struct
 /* Open a file stream */
 int _DtGrOpenFile(
     _DtGrStream *stream,
-    const char  *path
+    char        *path
 );
 
 /* Open a buffer stream */