canvas: alloc a sprite
Revert "canvas: alloc a sprite"

This reverts commit f54fc5bd5714f639a0685d28249db0bac2c1ab23.
Revert "canvas: alloc a sprite using the free-list"

This reverts commit 650efe9b2a2d5cbeba9fc0288713d2277301d6cb.
Revert "canvas: remove the shown/hidden list"

This reverts commit 11b2979f4b9668a4b8609be3a7c6f316a9ac8620.
Revert "doc: remove the shown list"

This reverts commit a5f5d9e185c4ea241ee314bea71796b378765061.
Revert "canvas: put free linked list in sprites struct"

This reverts commit 77a911863ee3ef09ca663f5bd806147dfc96c28a.
Revert "doc: update sprites struct."

This reverts commit bf0daa4cf35d21a54d590be49bbb56e53f4ae72c.
canvas: working on alloc,free,draw...