[8u] RFR 8170681: Remove fontconfig header files from JDK source tree

[Dmitry Cherepanov]

Please review/approve the backport of 8170681 to 8u-dev

JBS: https://bugs.openjdk.java.net/browse/JDK-8170681
Webrev (root repo): http://cr.openjdk.java.net/~dcherepanov/8170681/v0/webrev.root/
Webrev (jdk repo): http://cr.openjdk.java.net/~dcherepanov/8170681/v0/webrev.jdk/

The original patch doesn't apply cleanly to 8u-dev so it includes the following modifications
 - In 9, the fix for JDK-8138761 includes refactoring that splits libraries.m4 into several files (file per tool). For 8u-dev, the backport patch updates the existing libraries.m4 for consistency.
 - The original patch removes fontconfig.md with fontconfig license entry. For 8u-dev, the backport patch updates THIRD_PARTY_README files (for all repos).

Testing - repo with the patch builds on Windows/Mac. Also tested it on CentOS with and without fontconfig-devel installed.

Thanks,

Dmitry