(svn r13226) -Feature: Allow to have more than only two airports per town. The number of airports is now controlled by the noise each of them generates, the distance from town's center and how tolerant the town is.

Initial concept : TTDPatch (moreairpots),  Initial code : Pasky
Thanks to BigBB (help coding), Smatz Skidd13 and frosch for bugcatches and advices

src/town_cmd.cpp

@@ -1490,6 +1490,8 @@ static void DoCreateTown(Town *t, TileIndex tile, uint32 townnameparts, TownSize
 			break;
 	}
 
+	t->noise_reached = 0;
+
 	t->num_houses += x;
 	UpdateTownRadius(t);
 
@@ -1578,7 +1580,7 @@ Town *CreateRandomTown(uint attempts, TownSizeMode mode, uint size)
 	return NULL;
 }
 
-static const byte _num_initial_towns[4] = {5, 11, 23, 46};
+static const byte _num_initial_towns[4] = {5, 11, 23, 46};  // very low, low, normal, high
 
 bool GenerateTowns()
 {