--portable-native-sync and error handling

[Steven Augart]

It turns out that "glib"'s g_critical() facility, used
to report serious problems, calls g_log(), which then goes ahead
and calls the g_thread functions again.  Which are the very ones
that are trying to report the problem.

I've switched the error reporting in the --portable-native-sync
back to using the equivalent of fprintf(stderr, ...).

I've also gone back to using old-fashioned assert() instead of glib's
g_assert().


--
Steven Augart

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