1.3.2 - C++11 compatibility fix.

UPDATE: New High-Value Functionality will in the future be ported into this C++11 branch. https://github.com/KjellKod/g3log/tree/c++11-master

Changes with 1.3.2.

g3log v.1.3.1 had a CMake error that stopped c++11 only compiler from building.
g3log v1.3.2 contains the corrected CMake files.

Thanks to @esdevcr for providing this patch correction.

As g3log goes forward the branch 1.3.x will be the "c++11 master branch" in case of future changes.