place the constructor level configuration within the COMPILE_MUTEX, to prevent half-constructed mappers from getting sucked into the compile() phase
place the constructor level configuration within the COMPILE_MUTEX,
to prevent half-constructed mappers from getting sucked into the compile()
phase


git-svn-id: 655ff90ec95d1eeadb1ee4bb9db742a3c015d499@6369 8cd8332f-0806-0410-a4b6-96f4b9520244

obeattie/sqlalchemy,obeattie/sqlalchemy,obeattie/sqlalchemy