RFR: 4797982: Setting negative size of JSplitPane divider leads to unexpected results.

[Prasanta Sadhukhan]

Setting JSplitPane divider size to negative value leads to unexpected results and is not desirable and seems to be not practical.
I guess we should return IAE but it might break existing app so fixed to clamp it to 0 incase negative value is tried to be set for divider size.

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Commit messages:
 - Fix
 - 4797982: Setting negative size of JSplitPane divider leads to unexpected results.
 - 4797982: Setting negative size of JSplitPane divider leads to unexpected results.

Changes: https://git.openjdk.org/jdk/pull/9566/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9566&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-4797982
  Stats: 62 lines in 2 files changed: 62 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9566.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9566/head:pull/9566

PR: https://git.openjdk.org/jdk/pull/9566