Cody/other-devels, could you please see whether this fixes #2835 .  The bl20_lumped.i was failing on MountainLion, but i have not got access to that OSX here.  I also suspect that bl22_lumped was failing, but that is a heavy test.  amended gravity_head/tests with increased abs_zero.
Merge pull request #3013 from WilkAndy/feature_2835

Cody/other-devels, could you please see whether this fixes #2835 .  The ...