RFR: JDK-8238239: java.lang.Record spec clarifications

[Vicente Romero]

Please review the fix for [1] at [2] along with the corresponding CSR at 
[3]. The fix pretends to clarify the specification for java.lang.Record. 
Please see the CSR for more detail,

Thanks,
Vicente
PS, thanks to John Rose for proposing this fix

[1] https://bugs.openjdk.java.net/browse/JDK-8238239
[2] http://cr.openjdk.java.net/~vromero/8238239/webrev.00/
[3] https://bugs.openjdk.java.net/browse/JDK-8238240