[RMG] Fix mingw build, fix some warnings

lib/rmg/CMapGenerator.cpp

@@ -470,7 +470,7 @@ int CMapGenerator::getPrisonsRemaning() const
 }
 void CMapGenerator::decreasePrisonsRemaining()
 {
-	prisonsRemaining = std::max (0, prisonsRemaining--);
+	prisonsRemaining = std::max (0, prisonsRemaining - 1);
 }
 
 void CMapGenerator::registerZone (TFaction faction)

lib/rmg/CRmgTemplateZone.cpp

@@ -1159,7 +1159,7 @@ void CRmgTemplateZone::createObstacles(CMapGenerator* gen)
 	{
 		possibleObstacles.push_back (std::make_pair(o.first, o.second));
 	}
-	boost::sort (possibleObstacles, [](obstaclePair &p1, obstaclePair &p2) -> bool
+	boost::sort (possibleObstacles, [](const obstaclePair &p1, const obstaclePair &p2) -> bool
 	{
 		return p1.first > p2.first; //bigger obstacles first
 	});
@@ -1184,7 +1184,7 @@ void CRmgTemplateZone::createObstacles(CMapGenerator* gen)
 	for (auto tile : boost::adaptors::reverse(tileinfo))
 	{
 		//fill tiles that should be blocked with obstacles or are just possible (with some probability)
-		if (gen->shouldBeBlocked(tile) || gen->isPossible(tile) && gen->rand.nextInt(1,100) < 60)
+		if (gen->shouldBeBlocked(tile) || (gen->isPossible(tile) && gen->rand.nextInt(1,100) < 60))
 		{
 			//start from biggets obstacles
 			for (int i = 0; i < possibleObstacles.size(); i++)
@@ -1967,4 +1967,4 @@ void CRmgTemplateZone::addAllPossibleObjects (CMapGenerator* gen)
 void ObjectInfo::setTemplate (si32 type, si32 subtype, ETerrainType terrainType)
 {
 	templ = VLC->objtypeh->getHandlerFor(type, subtype)->getTemplates(terrainType).front();
-}
+}