On GCC 4.7.2, on ubuntu system, setting CMAKE_CXX_FLAGS
causes a compilation to fail (no input file)
Use add_definitions instead when selecting std=c++11 and adding Wall


Signed-off-by: Bartek Taczala <w0lanto@gmail.com>
Adding missing library for cpp-netlib-http-client_test


Signed-off-by: Bartek Taczala <w0lanto@gmail.com>