webos-image: Update layer pins for 2013-08-01

meta-webos as of 2013-08-01 16:51:13 -0700

915f349 gtest: Add recipe for v1.6.0
a02ca13 webos-image: libpbnjson=18

Open-webOS-DCO-1.0-Signed-off-by: Susan Montooth <susan.montooth@lge.com>