[API CHANGE] Have XCanvas provide all-surface erase-to-color.

And to make the names more telling, rename the old clear() method
to erase(), add new fill() for providing a color.
Cleanse sd of cppcanvas helper use.

In preparation of killing that very module.

Change-Id: I728e585a972eecdfb51050492b0962a140afa3ec
Kill remaining linker usages of cppcanvas.

Change-Id: I6b3a2de5a923abe4a49ac2bfd7610e16066d27e9
Rework slideshow to use XCanvas directly. Kill cppcanvas references.

This builds now, but is not working yet ...

Change-Id: I9995fe8cdbb0b8ca1be8d73a678feeb2c3708c9e
Die, wrapper code, die.

Change-Id: I987703958621abb38d877b3089aaaa7d0f97f5e9
[API CHANGE] Avoid excessive compound struct use for XCanvas.

Avoid excessive use of compound structures like integer or real
number sizes for bitmap or sprite creation. Everyone has to convert
into temporary UNO API compound structs at call sites otherwise,
let's skip that waste.

Change-Id: Ia242175334a48deabaf081675306377c1ba4322c
Wrap up plain XCanvas with view-specific render state.

Since XCanvas is stateless, we'd need to convey some state around,
e.g. transformations and clips.

Change-Id: I96ce2f4f1ab97c139e09938555d53f4f1edd2c02