[OpenJDK 2D-Dev] RFR: 8199530 : Upgrade to harfbuzz 1.7.6

[Phil Race]

Bug: https://bugs.openjdk.java.net/browse/JDK-8199530
Webrev: http://cr.openjdk.java.net/~prr/8199530/

We are currently using harfbuzz 1.7.1. This change updates to use 1.7.6

-phil.