RFR: JDK-8016524: [macosx] Bottom line is not visible for JTableHeader

[Harshitha Onkar]

A new test case was added to test the fix as there was no corresponding test case present for this issue previously.

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

Commit messages:
 - incorporated review changes
 - removed jtreg author tag
 - added copyright year and removed commented lines
 - Merge branch 'master' into JTableHeader_8016524
 - JtableHeader Bottom line issue fix

Changes: https://git.openjdk.java.net/jdk/pull/7219/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7219&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8016524
  Stats: 118 lines in 2 files changed: 116 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7219.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7219/head:pull/7219

PR: https://git.openjdk.java.net/jdk/pull/7219