This patch adds a new client utility that enables or disables plugin
features. The utility disables or enables a plugin using values (name,
soname, and symbols) provided via a configuration file by the same name.
For example, to ENABLE the daemon_example plugin, the utility will read
the daemon_example.ini configuration file and use the values contained to
enable or disable the plugin.
Put descriptions of plugins into a separate file read by MTR
MTR itself has generalised code to read this and set env. variables
Removed the *SO variables, updated some tests accordingly
New commit: added optional list of plugin names for _LOAD variable
Also made changes for the new AUTH_* plugins