[build] Set C++14 as default standard for CMake

CMakeLists.txt

@@ -1,5 +1,6 @@
 cmake_minimum_required(VERSION 3.1)
 project(mbgl LANGUAGES CXX C)
+set(CMAKE_CXX_STANDARD 14)
 
 include(cmake/mbgl.cmake)
 
@@ -44,6 +45,11 @@ if(APPLE)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-error=unused-command-line-argument")
 endif()
 
+if(CMAKE_COMPILER_IS_GNUCXX)
+    # https://svn.boost.org/trac/boost/ticket/9240
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fext-numeric-literals")
+endif()
+
 if(NOT EXISTS ${CMAKE_SOURCE_DIR}/platform/${MBGL_PLATFORM}/config.cmake)
     message(ERROR "Can't find config.cmake file for platform ${MBGL_PLATFORM}")
 endif()