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

[Liu, Xin]

Hi, Dmitry,
For your backport,  I think jdk8u also need to backport this one.
https://bugs.openjdk.java.net/browse/JDK-8192854

If users specify –with-fontconfig, buildscript is supposed to use ‘FONTCONFIG_CFLAGS’ to discover the header file fontconfig/fontconfig.h.  If you ignore FONTCONFIG_CFLAGS,  it will fall back to pick up from /usr/include. It’s fine by almost Linux distros.  We(Amazon) put 3rd libraries in non-standard location.  That why we have this problem.

webrev for backport JDK-8192854
https://cr.openjdk.java.net/~xliu/8192854/webrev/

thanks,
--lx