[SDL] DirectX Keymap - DIK_OEM_102

[Sam Lantinga]

> in SDL_dx5events.c: 
> both DIK_OEM_102 and DIK_BACKSLASH are mapped to SDLK_BACKSLASH:

> DIK_keymap[DIK_BACKSLASH] = SDLK_BACKSLASH;
> DIK_keymap[DIK_OEM_102] = SDLK_BACKSLASH;

I think there was a particular keyboard on which it was a backslash...
I'm okay with your proposed change, but can anyone else who has this key
comment on this?

Thanks!
	-Sam Lantinga, Software Engineer, Blizzard Entertainment