Fix module event prioritization which was broken with the newer

auto-attach event stuff.

Also remove logically dead code from os_defcon, and make os_defcon akill
similar masks to os_session when enforcing session akills.

Fixes #1618 which relies on os_session to be prioritized before
os_defcon.

src/module.cpp

@@ -101,6 +101,10 @@ void Module::SetAuthor(const Anope::string &nauthor)
 	this->author = nauthor;
 }
 
+void Module::Prioritize()
+{
+}
+
 ModuleVersion::ModuleVersion(int maj, int min, int pa) : version_major(maj), version_minor(min), version_patch(pa)
 {
 }