Make txn->abort work without bombing out for {{{test_txn_abort5}}} one case. Fixes #431.
 Start writing {{{test_txn_abort6}}}.   Addresses #443.
 Try to write a test for #399 and #400, but haven't managed to reproduce the problem.  Addresses #399, #400.
 Write a test for #332.  Addresses #332.


git-svn-id: file:///svn/tokudb@2406 c7de825b-a66e-492c-adef-691d508d4ae1