Remove all use of state_t from demo

This is the last step. We should be able to bury the API now.

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Bury state_t

We can now operate directly on draw ops and targets to set all the same drawing
parameters. We no longer need to encapsulate states themselves from the API.

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>