On left side of an assgnment YY_CURRENT_BUFFER should became YY_CURRENT_BUFFER_LVALUE.

This commit was SVN r2701.

src/util/show_help_lex.l

@@ -56,7 +56,7 @@ int ompi_show_help_finish_parsing(void)
 {
     if (NULL != YY_CURRENT_BUFFER) {
         yy_delete_buffer(YY_CURRENT_BUFFER); 
-        YY_CURRENT_BUFFER = NULL;
+        YY_CURRENT_BUFFER_LVALUE = NULL;
     }
     return YY_NULL;
 }