build,libweston: Use struct timespec for animations

build,libweston: Use struct timespec for animations

Change code related to animations to use struct timespec to represent
time.

This commit is part of a larger effort to transition the Weston codebase
to struct timespec.

Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
This bumps the libweston major version due to breakage in the animation
ABI. The commits following this one break more ABI in other parts.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>