Simple logging support
Write a message to stderr if verbose logging is on.
Write a message to stderr, prefixed with "warning: ".
If set, record all log messages (at all levels) in memory and dump to this directory on error. Useful for tracking down intermittent bugs.
Dump all recorded log entries to the crash handler set with set_crash_handler
.
If there is no handler, or the log is empty, does nothing. This is called automatically
after logging at level Warning.