msg: fix "error" parsing when DEBUG string is empty.
fix handling of external signals.

i.e. ignore them.   we don't care if, for example, the user
interrupts and resumes execution of the inferior.
vis2d: simplify vis part.

errors are checked for up front, no need to check for them again
before we pass the data along.
gfx: fix texturing parameters.
gfx: ... actually normalize.

not sure how commenting this out made it into a commit.
properly bail on error.

something will blow up after if we don't.