Remove: ENABLE_NETWORK switch

This switch has been a pain for years. Often disabling broke
compilation, as no developer compiles OpenTTD without, neither do
any of our official binaries.

Additionaly, it has grown so hugely in our codebase, that it
clearly shows that the current solution was a poor one. 350+
instances of "#ifdef ENABLE_NETWORK" were in the code, of which
only ~30 in the networking code itself. The rest were all around
the code to do the right thing, from GUI to NewGRF.

A more proper solution would be to stub all the functions, and
make sure the rest of the code can simply assume network is
available. This was also partially done, and most variables were
correct if networking was disabled. Despite that, often the #ifdefs
were still used.

With the recent removal of DOS, there is also no platform anymore
which we support where networking isn't working out-of-the-box.

All in all, it is time to remove the ENABLE_NETWORK switch. No
replacement is planned, but if you feel we really need this option,
we welcome any Pull Request which implements this in a way that
doesn't crawl through the code like this diff shows we used to.

src/script/api/script_admin.cpp

@@ -135,7 +135,6 @@
 	std::string json;
 	ScriptAdmin::MakeJSON(vm, -1, SQUIRREL_MAX_DEPTH, json);
 
-#ifdef ENABLE_NETWORK
 	if (json.length() > NETWORK_GAMESCRIPT_JSON_LENGTH) {
 		ScriptLog::Error("You are trying to send a table that is too large to the AdminPort. No data sent.");
 		sq_pushinteger(vm, 0);
@@ -143,7 +142,6 @@
 	}
 
 	NetworkAdminGameScript(json.c_str());
-#endif /* ENABLE_NETWORK */
 
 	sq_pushinteger(vm, 1);
 	return 1;

src/script/api/script_client.cpp

@@ -16,7 +16,6 @@
 
 #include "../../safeguards.h"
 
-#ifdef ENABLE_NETWORK
 /**
  * Finds NetworkClientInfo given client-identifier,
  *  is used by other methods to resolve client-identifier.
@@ -29,46 +28,29 @@ static NetworkClientInfo *FindClientInfo(ScriptClient::ClientID client)
 	if (!_networking) return NULL;
 	return NetworkClientInfo::GetByClientID((::ClientID)client);
 }
-#endif
 
 /* static */ ScriptClient::ClientID ScriptClient::ResolveClientID(ScriptClient::ClientID client)
 {
-#ifdef ENABLE_NETWORK
 	return (FindClientInfo(client) == NULL ? ScriptClient::CLIENT_INVALID : client);
-#else
-	return CLIENT_INVALID;
-#endif
 }
 
 /* static */ char *ScriptClient::GetName(ScriptClient::ClientID client)
 {
-#ifdef ENABLE_NETWORK
 	NetworkClientInfo *ci = FindClientInfo(client);
 	if (ci == NULL) return NULL;
 	return stredup(ci->client_name);
-#else
-	return NULL;
-#endif
 }
 
 /* static */ ScriptCompany::CompanyID ScriptClient::GetCompany(ScriptClient::ClientID client)
 {
-#ifdef ENABLE_NETWORK
 	NetworkClientInfo *ci = FindClientInfo(client);
 	if (ci == NULL) return ScriptCompany::COMPANY_INVALID;
 	return (ScriptCompany::CompanyID)ci->client_playas;
-#else
-	return ScriptCompany::COMPANY_INVALID;
-#endif
 }
 
 /* static */ ScriptDate::Date ScriptClient::GetJoinDate(ScriptClient::ClientID client)
 {
-#ifdef ENABLE_NETWORK
 	NetworkClientInfo *ci = FindClientInfo(client);
 	if (ci == NULL) return ScriptDate::DATE_INVALID;
 	return (ScriptDate::Date)ci->join_date;
-#else
-	return ScriptDate::DATE_INVALID;
-#endif
 }

src/script/api/script_clientlist.cpp

@@ -19,18 +19,15 @@
 
 ScriptClientList::ScriptClientList()
 {
-#ifdef ENABLE_NETWORK
 	if (!_networking) return;
 	NetworkClientInfo *ci;
 	FOR_ALL_CLIENT_INFOS(ci) {
 		this->AddItem(ci->client_id);
 	}
-#endif
 }
 
 ScriptClientList_Company::ScriptClientList_Company(ScriptCompany::CompanyID company)
 {
-#ifdef ENABLE_NETWORK
 	if (!_networking) return;
 	CompanyID c;
 	if (company == ScriptCompany::COMPANY_SPECTATOR) {
@@ -45,5 +42,4 @@ ScriptClientList_Company::ScriptClientList_Company(ScriptCompany::CompanyID comp
 	FOR_ALL_CLIENT_INFOS(ci) {
 		if (ci->client_playas == c) this->AddItem(ci->client_id);
 	}
-#endif
 }

src/script/api/script_game.cpp

@@ -39,9 +39,5 @@
 
 /* static */ bool ScriptGame::IsMultiplayer()
 {
-#ifdef ENABLE_NETWORK
 	return _network_server;
-#else
-	return false;
-#endif
 }

src/script/api/script_goal.cpp

@@ -137,12 +137,8 @@
 {
 	EnforcePrecondition(false, ScriptGame::IsMultiplayer());
 	EnforcePrecondition(false, ScriptClient::ResolveClientID(client) != ScriptClient::CLIENT_INVALID);
-#ifdef ENABLE_NETWORK
 	ClientIndex c = NetworkClientInfo::GetByClientID((::ClientID)client)->index;
 	return DoQuestion(uniqueid, c, true, question, type, buttons);
-#else
-	return false;
-#endif
 }
 
 /* static */ bool ScriptGoal::CloseQuestion(uint16 uniqueid)

src/script/api/script_object.cpp

@@ -301,10 +301,8 @@ ScriptObject::ActiveInstance::~ActiveInstance()
 	/* Are we only interested in the estimate costs? */
 	bool estimate_only = GetDoCommandMode() != NULL && !GetDoCommandMode()();
 
-#ifdef ENABLE_NETWORK
 	/* Only set p2 when the command does not come from the network. */
 	if (GetCommandFlags(cmd) & CMD_CLIENT_ID && p2 == 0) p2 = UINT32_MAX;
-#endif
 
 	/* Try to perform the command. */
 	CommandCost res = ::DoCommandPInternal(tile, p1, p2, cmd, (_networking && !_generating_world) ? ScriptObject::GetActiveInstance()->GetDoCommandCallback() : NULL, text, false, estimate_only);