- resorted some of thingdef.cpp's contents into more appropriate files.

- split FinishActor into several functions. While DECORATE can, ZSCRIPT cannot do all this in one go.
- split the state finalization into several class-specific virtual functions.

src/g_shared/a_weapons.cpp

@@ -67,6 +67,38 @@ void PClassWeapon::ReplaceClassRef(PClass *oldclass, PClass *newclass)
 	}
 }
 
+void PClassWeapon::Finalize(FStateDefinitions &statedef)
+{
+	Super::Finalize(statedef);
+	FState *ready = FindState(NAME_Ready);
+	FState *select = FindState(NAME_Select);
+	FState *deselect = FindState(NAME_Deselect);
+	FState *fire = FindState(NAME_Fire);
+
+	// Consider any weapon without any valid state abstract and don't output a warning
+	// This is for creating base classes for weapon groups that only set up some properties.
+	if (ready || select || deselect || fire)
+	{
+		if (!ready)
+		{
+			I_Error("Weapon %s doesn't define a ready state.", TypeName.GetChars());
+		}
+		if (!select)
+		{
+			I_Error("Weapon %s doesn't define a select state.", TypeName.GetChars());
+		}
+		if (!deselect)
+		{
+			I_Error("Weapon %s doesn't define a deselect state.", TypeName.GetChars());
+		}
+		if (!fire)
+		{
+			I_Error("Weapon %s doesn't define a fire state.", TypeName.GetChars());
+		}
+	}
+}
+
+
 //===========================================================================
 //
 // AWeapon :: Serialize