[2.6.x] Cherry-pick decoding bug fixes to 2.6.x?

[Simon McVittie]

Should the 2.6.x branch get cherry-picks of #547, #549?

[Ozkan Sezer]

These are also 1a48518, bcf314d, and 0cd9047.

But we should just make a new 2.8 release from the SDL2 branch, instead.

[Sam Lantinga]

I'm planning to make new SDL2 satellite library releases this month.