Consistently name every hookset with prefix hooks_. NFC.

I'm sure this causes massive merge-conflicts in the non-public code,
but I think it'd be a good idea, if only to avoid confusion between
e.g. `clearMemory` and the-variable-formerly-known-as `clearmemory`.

complex2.cpp

@@ -198,7 +198,7 @@ EX namespace brownian {
     vector<cell*> to_remove;
     for(auto p: futures) if(is_cell_removed(p.first)) to_remove.push_back(p.first);
     for(auto r: to_remove) futures.erase(r);
-    }) + addHook(clearmemory, 0, [] () { futures.clear(); })
+    }) + addHook(hooks_clearmemory, 0, [] () { futures.clear(); })
     + addHook(hooks_gamedata, 0, [] (gamedata* gd) { gd->store(futures); });
 
 EX }