JDK 13 RFR of JDK-8146726 : Improve AbstractProcessor to issue warnings for repeated information

[Joe Darcy]

Hello,

Returning to JDK-8146726, based on previous review feedback I've changed 
the title to "Improve AbstractProcessor to issue warnings for repeated 
information" and reworked the fix:

     http://cr.openjdk.java.net/~darcy/8146726.4/

Thanks,

-Joe