Draw now has its own staging buffer to use with its scrap. Also, a few
fixes were needed for the staging buffer and scrap flush routines.
Other than some synchronization issues with draw scrap flushing
(currently worked around with a fence-wait) things seem to be working
nicely.
The scrap texture did very good things for the glsl renderer and the
better control over data copying might help it do even better things for
vulkan, especially with lots of little icons.
First pixels! This was a nightmare of little issues that the validation
layers couldn't help with: incorrect input assembly, incorrect vertex
attribute specs. Though the layers did help with getting the queues
working. Still, lots of work to go but this is a major breakthrough as
I now have access to visual debugging for textures and the like.
Short wrappers for Draw functins are in vid_render_vulkan.c so the
vulkan context can be passed on to the actual functions. The 2D shaders
are set up similar to those in glsl, but with full 32-bit color (rgba)
support instead of paletted. However, the textures are not loaded yet,
nor is anything bound.
