#2130 Allow PETSc 3.3 to malloc new non-zeroes in special cases

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@18120 b5f69653-2bf5-0310-8201-b0dafb8e1405
#1660 beef up HDF5 reader test.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@18121 b5f69653-2bf5-0310-8201-b0dafb8e1405