tests: bring in gtest-1.6.0

Bundled in gtest-1.6.0 from
http://code.google.com/p/googletest/downloads/list

Main CMakeLists.txt modified to include it in case tests are enabled.

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <norluk@luxoft.com>
Change-Id: Ib33cb25b3c64b74306ef24fe7420033f2cba7a09
Reviewed-on: https://g2g.palm.com/2244
Reviewed-by: Build Verification
Reviewed-by: Nikolay Orliuk <norluk@luxoft.com>
Tested-by: Nikolay Orliuk <norluk@luxoft.com>
Reviewed-by: Maksym Sditanov <msditanov@luxoft.com>
Tested-by: Maksym Sditanov <msditanov@luxoft.com>
Reviewed-by: Roger Stringer <roger.stringer@lge.com>