Partial work on making the striped decoding optional

IE 11 in Windows 8.1 update 1 fixes luminance texture support
so we can drop the stripe and use the byte textures directly.

Todo: fall back to the striped mode on IE 10 and IE 11 pre-update
Disable debug
Merge branch 'master' into destripe
Drop stripe texture from JS support

This means IE 10 won't use WebGL, but IE 11 update 1 will.
Autodetection now checks for luminance texture support.
Remove Flash GPU rendering, not worth the effort

It relied on the stripe texture *and* didn't do
any sensible scaling. Ick! Just drop it.
Linear subsampling on chroma for prettiness

Thanks to killing the stripe texture usage.
Merge pull request #109 from brion/destripe

Don't use the stripe texture when we don't need it