GitLab

Adds threading support (by Miklos Fazekas, Vlad Losev, and Chandler Carruth); adds wide InitGoogleTest to gtest.def (by Vlad Losev); updates the version number (by Zhanyong Wan); updates the release notes for 1.5.0 (by Vlad Losev); removes scons scripts from the distribution (by Zhanyong Wan); adds the cmake build script to the distribution (by Zhanyong Wan); adds fused source files to the distribution (by Vlad Losev and Chandler Carruth).

Fixes: Scons build file broken when used in another SConstruct; warning in VC 8.0 when compiled with /Wp64