#2481 Attempt Mavericks fix.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21725 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2481 Another go at a Mavericks fix

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21733 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2434 Minor change to mutable mesh to allow deletion of elements

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21749 b5f69653-2bf5-0310-8201-b0dafb8e1405