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/protocol.h

@@ -301,8 +301,8 @@ public:
             READWRITE(nTime);
         uint64_t nServicesInt = nServices;
         READWRITE(nServicesInt);
-        nServices = (ServiceFlags)nServicesInt;
-        READWRITE(*(CService*)this);
+        nServices = static_cast<ServiceFlags>(nServicesInt);
+        READWRITE(*static_cast<CService*>(this));
     }
 
     // TODO: make private (improves encapsulation)