film_grain.data field of Dav1dFrameHeader is not 16-byte-aligned, causing segfault on x86 decode attempts

These two locations in the x86 assembly require 16-byte-alignment of the indirect counter's address: https://code.videolan.org/videolan/dav1d/blob/master/src/x86/film_grain_ssse3.asm#L484 https://code.videolan.org/videolan/dav1d/blob/master/src/x86/film_grain_ssse3.asm#L1096 But the operand is not guaranteed such alignment. Though 0xb0 is a multiple of 16, the fg_data address is not; even if the Dav1dFrameHeader's address is aligned, there are 7 int fields before the film_grain.data subfield's location: https://code.videolan.org/videolan/dav1d/blob/master/include/dav1d/headers.h#L337

Result is segfault on x86 decode attempts involving film grain.