RFR : 8010948 : Add conversion functional interfaces

[Mike Duigou]

Hello all;

Another set of functional interfaces for review for the soon-to-be-arriving-in-TL-repo lambda libraries.

http://cr.openjdk.java.net/~mduigou/JDK-8010948/0/webrev/

These interfaces are Functions between the core primitive types (double, int, long) used by the lambda libraries. Methods providing the equivalent of the widening and narrowing primitive conversions may be added in a later patch.

Mike