Remove machine-specific IncludePath from SDL.vcxproj

These IncludePath values seem to not actually be needed since nobody
noticed they were wrong for the past couple months.

metal: avoid an extra buffer allocation and GPU data copy in RunCommandQueue, it's not needed. Improves overall performance.

metal: remove an obsolete section of a constant buffer.

fix build using Watcom :

./src/render/SDL_render.c(2168): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2168): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2175): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2175): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2322): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2322): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2322): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2322): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2329): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2329): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2329): Error! E1054: Expression must be constant
./src/render/SDL_render.c(2329): Error! E1054: Expression must be constant

./src/render/software/SDL_render_sw.c(602): Error! E1054: Expression must be constant
./src/render/software/SDL_render_sw.c(602): Error! E1054: Expression must be constant
./src/render/software/SDL_render_sw.c(602): Error! E1054: Expression must be constant
./src/render/software/SDL_render_sw.c(602): Error! E1054: Expression must be constant

merge fallout: Patched to compile, fixed some compiler warnings, etc.

Merge SDL-ryan-batching-renderer branch to default.

Closing SDL-ryan-batching-renderer branch.

joystick: Add Linux mappings for "Xbox One Wireless Controller (Model 1708)"

Adds controller bindings to support the "Xbox One Wireless Controller
(Model 1708)" on Linux. The Model 1708 was released in 2016 alongside the
Xbox One S. It is the current model being sold by Microsoft as of writing.
(October 22, 2018)

fix NetBSD C90 build failure

src/vendor/SDL2/src/joystick/bsd/SDL_sysjoystick.c:353:5: error:
ISO C90 forbids mixed declarations and code [-Werror=declaration-after-statement]

reported by 'bch' at https://discourse.libsdl.org/t/25231

Fix crash when GL_LoadFunctions()/GLES2_LoadFunctions() fails
https://bugzilla.libsdl.org/show_bug.cgi?id=4350

We can't safely call GL_DestroyRenderer() until GL_LoadFunctions()
succeeds because we will be missing functions that we try to use
when activating the renderer for destruction if we have an GL context.