cleanup. Deprecate init and cleanup; update PLUGIN_VERSION_CHECK
macro.
Add a debug message and fail to load a plugin if it has no
plugin_version_check() function.
Check that plugin keybinding names have been set in plugin_init(),
otherwise print a debug message and ignore all of them.


git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/trunk@2616 ea778897-0a13-0410-b9d1-a72fbfd435f5