Change the ADJUSTSTRETCH action to also support toggling.

Previously, pressing ADJUSTSTRETCH while alredy in time-stretch adjust
mode exited the mode.  Doing so now toogles the time-stretch speed.
SELECT and ESCAPE can be used to exit time-stretch adjust mode
instead.  This change allows convenient access to both adjusting and
toggling the time-stretch speed with a single key.

mythtv/libs/libmythtv/tv_play.cpp

@@ -4105,6 +4105,8 @@ bool TV::TimeStretchHandleAction(PlayerContext *ctx,
     else if (has_action(ACTION_UP, actions))
         ChangeTimeStretch(ctx, 5);
     else if (has_action("ADJUSTSTRETCH", actions))
+        ToggleTimeStretch(ctx);
+    else if (has_action(ACTION_SELECT, actions))
         ClearOSD(ctx);
     else
         handled = false;