This adds two functions for drivers to use directly to keep a
linked list of slave pixmaps to do damage tracking on and keep
updated. It also adds a helper function that drivers may optionally
call to do a simple copy area damage update.
v2: use damage.h not damagestr.h, fixes ephyr build.
v3: address ajax review: use slave_dst, drop unused dst member.
v4: check DamageCreate return, add SourceValidate comment,
add a comment addressing possible optimisation possibility
Reviewed-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
9b8217f9ef