even more attempts to fix hxcpp pch errors

more attempts to fix hxcpp pch errors

update sdl revision

void typedef; use specific naming for safety

fix void definitions for haxe 3.2/3.4 differences (iOS specific)

README; update with some extra information and tidying

Merge pull request #17 from gogoprog/patch-1

remove old include guards

Updated sample code in README.md

add tvOS defines alongside ios functionality

Keycodes; make sure they compile correctly with newer haxe rules

tidy up include guards, make sure hxcpp is first

better approach to minimum target

mac; Add required framework and ensure a sane deployment target minimum is set (defaults to 10.5 on sierra?, which gets errors on SDL_platform.h wanting 10.6)

update to sdl 2.0.5