[PATCH v2] Fix crash when a stencil routine is missing

[Patrick McCarty]

Hello,

I have updated my patchset on Rietveld:

http://codereview.appspot.com/83046/show

Thank you all for your reviews.  I have a few questions/concerns:

1.) I used Jan's suggestion for -d option name, but I'm not sure this
is the best name.  What should the option be called?

2.) Is backend-library.scm a suitable place for the "backend-testing" procedure?

3.) I don't know how to enable the -d option by default for regression
test compilation, so should I delegate this task?


Thanks,
Patrick