+- `common.h` is gone. Everything useful in it was moved to `ircd_defs.h`.
+- `config.h` is gone; the few remaining knobs in it were not for configuration
+ by mere mortals, and mostly existed as a 2.8 relic. Most of the knobs live in
+ `defaults.h`, but one is well-advised to stay away unless they know exactly
+ what they are doing.
+- A new module API has been introduced, known as AV2. It includes things such as
+ module datecodes (to ensure modules don't fall out of sync with the code),
+ module descriptions, and other fun things.
+- Alias and module commands are now in m_alias and m_modules, respectively, and
+ can be reloaded if need be. For sanity reasons, m_modules is a core module,
+ and cannot be unloaded.