Upgrade gtest to v 1.7.0?

[jenshnielsen]

This includes some fixes needed for c++11. Otherwise it breaks compilation.
After upgrading you will most likely need to nuke the build dir.

[jenshnielsen]

What seems to work for Mavericks is to upgrade to 1.7 and remove the cpp11 option
add_definitions(-DGTEST_LANG_CXX11) from FindGtest.cmake

[jenshnielsen]

The logic for this in 1.6 is complicated and possibly broken trying to load from tr1.