Add optional playing strength descriptions for AIs

* support the following numerical keys in JSON files for AIs:
  * "wins"
  * "losses"
  * "draws" (games without a winner after several hours of game time)

* keys contain data about playing strength of AIs relative to eath other

* if at least one key value is non-zero, calculate percentages and print
  these data in an extra line of AI tooltips with some translatable text

* fill out key values for NullBot and SemperFi JavaScript, based on an
  AI tournament by EuPhobos (forum username: Prot) from 23 October 2018,
  when its results were archived at https://archive.fo/QtSjR

Fixes Warzone2100#419

data/mp/multiplay/skirmish/nb_generic.json

@@ -4,6 +4,9 @@
         "name": "NullBot",
         "tip": "Adaptive AI with multiple personalities",
         "easy_tip": "Gets ~ 25% less power from each oil derrick\nResearch is not focused on a specific weapon branch",
-        "insane_tip": "Gets ~ 100% more power from each oil derrick\nStarts with defensive structures and oil derricks"
+        "insane_tip": "Gets ~ 100% more power from each oil derrick\nStarts with defensive structures and oil derricks",
+        "wins": 18927,
+        "losses": 12773,
+        "draws": 261
     }
 }

data/mp/multiplay/skirmish/semperfi-js.json

@@ -4,6 +4,9 @@
         "name": "SemperFi JavaScript",
         "tip": "Prototypical JavaScript AI focusing on rockets/missiles",
         "easy_tip": "Gets ~ 25% less power from each oil derrick",
-        "insane_tip": "Gets ~ 100% more power from each oil derrick\nStarts with defensive structures and oil derricks"
+        "insane_tip": "Gets ~ 100% more power from each oil derrick\nStarts with defensive structures and oil derricks",
+        "wins": 1806,
+        "losses": 2355,
+        "draws": 23
     }
 }

src/multiint.cpp

@@ -275,7 +275,7 @@ struct AIDATA
 	char slo[MAX_LEN_AI_NAME];
 	char vlo[MAX_LEN_AI_NAME];
 	char js[MAX_LEN_AI_NAME];
-	char tip[255];
+	char tip[255 + 128]; // may contain optional AI tournament data
 	char difficultyTips[4][255]; // optional difficulty level info
 	int assigned;	///< How many AIs have we assigned of this type
 };
@@ -811,6 +811,21 @@ void readAIs()
 			sstrcpy(ai.tip, _("MISSING AI DESCRIPTION"));
 		}
 
+		int wins = aiconf.value("wins", 0).toInt();
+		int losses = aiconf.value("losses", 0).toInt();
+		int draws = aiconf.value("draws", 0).toInt();
+		int total = wins + losses + draws;
+		if (total)
+		{
+			float win_percentage = static_cast<float>(wins) / total * 100;
+			float loss_percentage = static_cast<float>(losses) / total * 100;
+			float draw_percentage = static_cast<float>(draws) / total * 100;
+			sstrcat(ai.tip, "\n");
+			char statistics[127];
+			ssprintf(statistics, _("AI tournament: %3.1f%% wins, %3.1f%% losses, %3.1f%% draws"), win_percentage, loss_percentage, draw_percentage);
+			sstrcat(ai.tip, statistics);
+		}
+
 		if (strcmp(*i, "nb_generic.json") == 0)
 		{
 			aidata.insert(aidata.begin(), ai);