CXX-216 Update Travis (Clang 3.4 and GCC 4.8)
CXX-197 Backport server r2.6.0..r2.6.1 changes
CXX-204 Use vendored timegm implementation if platform does not offer it

(cherry picked from commit 5bf477aa3dee9e82c9c2286a9ad8341cd71dfe97)

Conflicts:
	SConstruct
	src/mongo/util/time_support.cpp
Merge branch '26compat' of github.com:mongodb/mongo-cxx-driver into 26compat