pkgconfig tweakish
Work in progress: split out YCbCr conversion

(adapted from old color-worker branch)
Switch from packed to unpacked ycbcr planes

Seems to have a very slight speed improvement on decoding vs packing them.
remove no longer needed params
Optimize YUV conversion for 4:2:2 and 4:2:0
Halve the time spent in TypedArray.set() in IE 11

Making the hopefully not unwarranted assumption that we can copy
as dwords instead of bytes from the ycbcr array.

IE's TypedArray.set() is horribly slow and seems to basically do
a for loop and set each element individually. Copying the ycbcr
frame buffers out 32 bits at a time seems to save noticeably.
whoops, stray debug line
Size selection -- same defaults, should work

todo: trim out transcodes that don't exist from the selector
Make audio buffer slightly smaller

Still big enough for audio on slow iPod