Big reorganisation:

* add lane type descriptors, to be used by the random data
  generators -- as-yet unused

* move existing tests into new groupings, and rename some of
  them to be more consistent with the new notation.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13936 a5019735-40e9-0310-863c-91ae7b9d1cf9