step 1 of WL#2761 - MySQL plugin interface. It includes a minimal subset of WL#2761 that allows to create a usable plugin: * C API * mysql.plugin table It does not include * a possibility to add new syntax, status variables, command line options * LOAD/UNLOAD/SHOW PLUGINS statements Still, the implementor may decide to implement anything that is listed as "not included", if it'll be necessary to (see above) "create a usable plugin"
see WL#2761
