i needs to be treated as signed to get the proper indexing on 64-bit
platforms. This behavior was accidentally reverted when fixing an
unsigned/signed comparison warning.
Change-Id: Ic306d609bdc8de94c8f8ba29c6e45c736101a82e
This doesn't play well with autotools, and the preprocessor magic is
confusing and unhelpful in the vp8-only context.
Change-Id: I2fcb57e6eb7876ecb58509da608dc21f26077ff1