The stack is arbitrary strings that the validation layer debug callback
prints in reverse order after each message. This makes it easy to work
out what nodes in a pipeline/render pass plist are causing validation
errors. Still have to narrow down the actual line, but the messages seem
to help with that.
Putting qfvPushDebug/qfvPopDebug around other calls to vulkan should
help out a lot, tool.
As a bonus, the stack is printed before debug_breakpoint is called, so
it's immediately visible in gdb.
Not only does it makes sense to centralize the setting of viewport and
scissor, but it's actually necessary in order to fix the upside-down
rendering on windows.
It now takes a context pointer (opaque data) that holds the buffers it
uses for the temporary strings. If the context pointer is null, a static
context is used (making those uses of va NOT thread-safe). Most calls to
va use the static context, but all such calls have been formatted
consistently so they are easy to find when it comes time to do a full
audit.
This paves the way for clean initialization of the Vulkan renderer, and
very much cleans up the older renderer initialization code as gl and sw
are no longer intertwined.
