Fix issue #1431 (Tx and NoTx used concurrently)

A new try with a OModificationLock new implementation that allow full reentrancy (read-read, read-write, write-write and write-read).
Ant tests pass:
   [testng] ===============================================
   [testng] Test Suite Example
   [testng] Total tests run: 999, Failures: 0, Skips: 0
   [testng] ===============================================


But I can't test maven test (not enough memory on my 32bits laptop).