postproc : Re-work posproc calling to allow more flags.

Debugging in postproc needs more flags to allow for specific
block types to be turned on or off in the visualizations.

Must be enabled with --enable-postproc-visualizer during
configuration time.

Change-Id: Ia74f357ddc3ad4fb8082afd3a64f62384e4fcb2d
12 files changed