[12] RFR: JDK-8214793: Update copyright header for files modified in 2018

[Kevin Rushforth]

Ambarish or Murali,

Please review the following fix to bump the copyright year to 2018 for 
files modified last year, but not updated:

https://bugs.openjdk.java.net/browse/JDK-8214793
http://cr.openjdk.java.net/~kcr/8214793/webrev/

Thanks.

-- Kevin