RFR: JDK-8273387: remove some unreferenced gtk-related functions [v3]

[Matthias Baesken]

> Please review this small change.
> Looks like there are a few functions, like gtk2_paint_diamond, that are unreferenced and can be removed.
> 
> Thanks, Matthias

Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:

  remove declaration

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5384/files
  - new: https://git.openjdk.java.net/jdk/pull/5384/files/627cffa0..46b90ad9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5384&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5384&range=01-02

  Stats: 4 lines in 1 file changed: 0 ins; 4 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5384.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5384/head:pull/5384

PR: https://git.openjdk.java.net/jdk/pull/5384