[8u] Request for approval: 8030987 sun_awt_X11_GtkFileDialogPeer.h can be removed

[Sergey Bylokhov]

Hello,
This is a direct back port from jdk 9 to jdk 8u.

Bug: https://bugs.openjdk.java.net/browse/JDK-8030987
Webrev can be found at: http://cr.openjdk.java.net/~serb/8030987/webrev.00
Review:
http://mail.openjdk.java.net/pipermail/awt-dev/2013-December/006740.html
jdk9 changeset: http://hg.openjdk.java.net/jdk9/jdk9/jdk/rev/f24bf3debb52

Reviewers: Petr Pchelko, Alexander Zvegintsev.