RFR:8143413:add toEpochSecond methods for efficient access

[nadeesh tv]

Hi all,

Please review a fix for

Bug Id -https://bugs.openjdk.java.net/browse/JDK-8143413 
<https://bugs.openjdk.java.net/browse/JDK-8143413>

Issue - add toEpochSecond methods for efficient access

webrev - http://cr.openjdk.java.net/~ntv/8143413/webrev.01/ 
<http://cr.openjdk.java.net/%7Entv/8143413/webrev.01/>

-- Thanks and Regards,
Nadeesh TV