(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/openttd.cpp

@@ -1345,6 +1345,11 @@ static bool InitializeWindowsAndCaches()
 
 	SetCachedEngineCounts();
 
+	/* Towns have a noise controlled number of airports system
+	 * So each airport's noise value must be added to the town->noise_reached value
+	 * Reset each town's noise_reached value to '0' before. */
+	UpdateAirportsNoise();
+
 	return true;
 }