Latest Gerris changes

From Gerris

The latest Gerris version is 2013-01-12 including the following 5 changes changes:

2013-01-10 Stephane Popinet <s.popinet at gmail.com>
  * Fixes for convergence checks for Boyd's culvert model

2013-01-10 Stephane Popinet <s.popinet at gmail.com>
  * Checks that SourcePipe does not use negative water depths

2013-01-12 Stephane Popinet <popinet at users.sf.net>
  * Fixed scaling of 'geo' test case

2013-01-12 Stephane Popinet <popinet at users.sf.net>
  * Cosmetics for Rossby test case

2013-01-12 Stephane Popinet <popinet at users.sf.net>
  * New test case geostrophic adjustment with Saint Venant