Correct formats creating depth texmaps

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Use a texmap as a depth buffer

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Don't double-free outgoing colorbuf in colorbuf_prep

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Gather to an intermediate buffer

This will allow us to, hopefully, do depth peeling, as we can hit the target
multiple times.

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Learn to stop worrying and love Autotools

Handmade Makefiles were great, but early reception indicates that the
compatibility issues automake panics about are at least partially real. This
also gets us the (always planned) config script for cheap. The conversion was
actually nearly painless. Everything builds as expected.

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