fix init

[jagprog5]

The SDL image library can initialize the codecs up front for whatever formats. this is done by calling IMG_Init.

However, it is not necessary. All of the image format that sdl2 support have the same pattern, like here for png, or here for jpg. Before loading the image it will try to load the codec if it is not already loaded.

So a pattern that can be used is:

1. init with no flags
2. then on load_texture it will link the codecs as needed, whenever an image of that format is loaded

of note: this is explicitly valid in the docs.

it's legal to call this with zero (no flags set)

Right now via rust bindings, calling

sdl2::image::init(sdl2::image::InitFlag::empty())

gives the cryptic error: "Could not init: ", which is... interesting.

and also, current logic uses, intersects, but this gives success if any of the libs init correctly (but even if one fail then it's not propagated to the caller!), when it should instead give fail only if any of them fail.

[Cobrand]

Looks good, but add this to the changelog since there is probably someone out there who will have their code break because of this change.