Use static_cast instead of C-style casts for non-fundamental types

A C-style cast is equivalent to try casting in the following order:

1. const_cast(...)
2. static_cast(...)
3. const_cast(static_cast(...))
4. reinterpret_cast(...)
5. const_cast(reinterpret_cast(...))

By using static_cast<T>(...) explicitly we avoid the possibility
of an unintentional and dangerous reinterpret_cast. Furthermore
static_cast<T>(...) allows for easier grepping of casts.

src/httpserver.cpp

@@ -512,7 +512,7 @@ struct event_base* EventBase()
 static void httpevent_callback_fn(evutil_socket_t, short, void* data)
 {
     // Static handler: simply call inner handler
-    HTTPEvent *self = ((HTTPEvent*)data);
+    HTTPEvent *self = static_cast<HTTPEvent*>(data);
     self->handler();
     if (self->deleteWhenTriggered)
         delete self;