This patch updates the googletest download link to point to
googletest's new home at:
https://github.com/google/googletest/archive/

The patch also upgrades to version 1.8 of googletest.
Partly because versions 1.6 and 1.7 now consists of
two separate .zip files (googletest + googlemock),
while 1.8 still contains both in one.

Since googletest 1.8 does not compile with
SunStudio12u2, gunit tests are now disabled if compiled
on Solaris with anything older than Solaris Studio 12.4.