FlxG: Add macro to determine VERSION

[Geokureli]

I hate doing this manually

made using: https://gist.github.com/Geokureli/9d0ac4598aa595b79f43919850601701

[Cheemsandfriends]

I have some concerns with this

Does this mean we have to compile with internet access at all times if we're downloading flixel from Haxelib?

[Geokureli]

I have some concerns with this

Does this mean we have to compile with internet access at all times if we're downloading flixel from Haxelib?

No, this works the same way as #if (flixel < version("5.3.0")) because the value of the flixel flag is its version. as for the git sha, that already existed in the old code