MYSQLD.

DESCRIPTION
===========
Crash occurs when daemon_example plugin is uninstalled
immediately after its installed. This can be reproduced
by installing and uninstalling the plugin repeatedly.

ANALYSIS
========
The daemon_example_plugin_deinit() function of the daemon
example plugin calls pthread_cancel() but doesn't wait for
the worker thread to actually complete before deallocating
the data buffer and closing the file that it writes to.
This is causing SEGFAULT!

FIX
===
Added a pthread_join() to wait for the thread to complete
before doing the cleanup work.

Removed a stray 'x' variable from the example code.

NOTE
====
Have made an entry in .opt file as given below:
--plugin-dir=$DAEMONEXAMPLE_DIR

This is done so that the program takes plugin directory as
../<dbg>/plugin/daemon_example/ instead of
../lib/plugin/