Comment 5 for bug 927539

This appears to have become a fatal (or at least very verbose) error in petsc-dev so I've locally implemented a very simple and naive implementation to get around it (see linked branch). Would appreciate some feedback on it to make it mergeable.

In particular:
 - this now happens automatically when using the standard assembler, should it be optional as suggested above and if so where would that option go (subroutine parameter or global)?
 - I've only modified the standard assembler and not the openmp assembler, should it go there too?
 - as this bug only affects the petsc backend should it only happen when using petsc?
 - any other comments/suggestions?

Run through of dolfin tests for linked branch available at:
http://diana.apam.columbia.edu:8010/builders/dolfin-x86-64-diag/builds/0/steps/shell_4/logs/stdio