20110421
  cplex.c: adjust basis manipulations so netopt=1 or netopt=2 may provide a
better starting basis for finishing the solution of a problem after CPLEX
has dealt with an embedded network.
  cplex.c, README.cplex:  adjust prestats to work independently of mipdisplay
and display.  Now prestats=1 causes summary statistics (if nonzero) for CPLEX's
"aggregate" and "presolve" algorithms to be reported in the solve_message.
Unfortunately, setting prestats=1 may disable use of multiple threads.
