2d9885c introduced some regressions. This addresses those.
* Don't throw return type notice or session write failure when in an exception
* Fix tests to properly return true/false since null is no longer falsy/successy
* Rerecord a few tests to accomodate difference in raised warnings
These were caused by the tests assuming default values for some session
configuration settings, in particular session.save_path and session.name.
The tests now explicitly set these settings in the --INI-- section.
These hopefully test a reasonable set of basic, error and variations for
the twenty or so session functions. Note however that they do not
test all the session configuration settings.
