message: cmake: enforce shadowing warnings
  Given the previously found bug we really need to enable warnings for
  shadowing.
diff: @@ -11,7 +11,7 @@ set(CMAKE_CXX_FLAGS_DEBUG "-DDEBUG")
  if(NOT MSVC)
  # Clang and GCC
  # We are not using exceptions to make it easier to write wrappers.
  - add_definitions("-std=c++11 -Wall -Wextra -Werror -fno-exceptions")
  + add_definitions("-std=c++11 -Wall -Wextra -Werror -fno-exceptions -Wshadow")
  set(platform_libs "pthread")
  set(curl_lib "curl")
  else()
  