RFR: JDK-8089986: Menu beeps when mnemonics used

[Dean Wookey]

Hi,

Please review the fix for JDK-8089986:  Menu beeps when mnemonics is used
https://bugs.openjdk.java.net/browse/JDK-8089986
https://github.com/javafxports/openjdk-jfx/pull/397

Dean