Doc: Describe limiting build output in the Compile Output pane

Change-Id: I1302d0554c8fd8d866a6280c45374802bd08f64d
Task-number: QTCREATORBUG-2200
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

doc/src/howto/creator-ui.qdoc

@@ -479,6 +479,8 @@
     when building applications, select \uicontrol Tools > \uicontrol Options >
     \uicontrol {Build & Run} > \uicontrol General, and then select the
     \uicontrol {Open Compile Output pane when building} check box.
+    In the \uicontrol {Limit build output to} field, you can specify the maximum
+    amount of build output lines to display in the pane.
 
     \section2 Debugger Console