Add release note for --no-compat flag

RELEASENOTES.docu

@@ -1730,4 +1730,11 @@ extern typedef struct { } my_type_t;</pre> </add-note></build-id>
       This warning is only enabled by default with Simics API version 7 or
       above. With version 6 and below it must be explicitly enabled by passing
       <tt>--warn=WLOGMIXUP</tt> to DMLC.</add-note></build-id>
+  <build-id value="next"><add-note> Added a flag <tt>--no-compat</tt>
+      to selectively disable compatibility features. In
+      particular, <tt>--no-compat=port_proxy_ifaces</tt> disables
+      generation of interface trampolines, which can speed up
+      compilation of devices with huge arrays of ports. The
+      option <tt>--help-no-compat</tt> lists all features that can be
+      disabled.</add-note></build-id>
 </rn>