factor out common functions in replay test
dump_cmdstream.py: ignore first 8 words in command buffer

The blob driver never bothers to write padding, this makes the output more clear
by not parsing uninitialized garbage.

Also label addresses with unique identifiers in the command stream.
companion cube replay

need to figure out texture format; texturing currently only functional with a
raw dump of the texture memory from the GL example
figure out texture tiling