Do not use the "debug" loglevel when built with NDEBUG.
model-checker : print depth of the counter-example in model checking statistics
model-checker : update tesh files
Remove debug messages from test, allow it to pass even with enable_debug=OFF.

Also add suffix "-thread" to tests with the thread context factory.
Add tests for ucontext and raw factory (storage, masterslave-virtual-machines).
Link fortran programs with libm.
With smpiff, give output file a sensible name.
tesh.pl: tesh input can be received on stdin, even with no args.
Try to fix mess with exit status.
Add name of failing function in error message.
Minor corrections in ChangeLog.