Log Message:
SDL2: update to 2.0.6

Changes 2.0.6:

General:
* Added cross-platform Vulkan graphics support in SDL_vulkan.h
        SDL_Vulkan_LoadLibrary()
        SDL_Vulkan_GetVkGetInstanceProcAddr()
        SDL_Vulkan_GetInstanceExtensions()
        SDL_Vulkan_CreateSurface()
        SDL_Vulkan_GetDrawableSize()
        SDL_Vulkan_UnloadLibrary()
  This is all the platform-specific code you need to bring up Vulkan on all SDL \ 
platforms. You can look at an example in test/testvulkan.c
* Added SDL_ComposeCustomBlendMode() to create custom blend modes for 2D rendering
* Added SDL_HasNEON() which returns whether the CPU has NEON instruction support
* Added support for many game controllers, including the Nintendo Switch Pro \ 
Controller
* Added support for inverted axes and separate axis directions in game \ 
controller mappings
* Added functions to return information about a joystick before it's opened:
        SDL_JoystickGetDeviceVendor()
        SDL_JoystickGetDeviceProduct()
        SDL_JoystickGetDeviceProductVersion()
        SDL_JoystickGetDeviceType()
        SDL_JoystickGetDeviceInstanceID()
* Added functions to return information about an open joystick:
        SDL_JoystickGetVendor()
        SDL_JoystickGetProduct()
        SDL_JoystickGetProductVersion()
        SDL_JoystickGetType()
        SDL_JoystickGetAxisInitialState()
* Added functions to return information about an open game controller:
        SDL_GameControllerGetVendor()
        SDL_GameControllerGetProduct()
        SDL_GameControllerGetProductVersion()
* Added SDL_GameControllerNumMappings() and SDL_GameControllerMappingForIndex() \ 
to be able to enumerate the built-in game controller mappings
* Added SDL_LoadFile() and SDL_LoadFile_RW() to load a file into memory
* Added SDL_DuplicateSurface() to make a copy of a surface
* Added an experimental JACK audio driver
* Implemented non-power-of-two audio resampling, optionally using libsamplerate \ 
to perform the resampling
* Added the hint SDL_HINT_AUDIO_RESAMPLING_MODE to control the quality of resampling
* Added the hint SDL_HINT_RENDER_LOGICAL_SIZE_MODE to control the scaling policy \ 
for SDL_RenderSetLogicalSize():
        "0" or "letterbox" - Uses letterbox/sidebars to fit \ 
the entire rendering on screen (the default)
        "1" or "overscan"  - Will zoom the rendering so it \ 
fills the entire screen, allowing edges to be drawn offscreen
* Added the hints SDL_HINT_MOUSE_NORMAL_SPEED_SCALE and \ 
SDL_HINT_MOUSE_RELATIVE_SPEED_SCALE to scale the mouse speed when being read \ 
from raw mouse input
* Added the hint SDL_HINT_TOUCH_MOUSE_EVENTS to control whether SDL will \ 
synthesize mouse events from touch events