Check floating point mode at startup

this detects wrong floating point modes which cause OOS
(http://gna.org/bugs/?24223) or even casue lua to crash, because lua relies
on IEEE 754 double precision and also on IEEE 754 nearest rounding.

src/wesnoth.cpp

@@ -514,6 +514,41 @@ static void handle_lua_script_args(game_launcher * game, commandline_options & /
 	}
 }
 
+#ifdef _WIN32
+static void check_fpu()
+{
+	uint32_t f_control;
+	if(_controlfp_s(&f_control, 0, 0) == 0) {
+		uint32_t unused;
+		uint32_t rounding_mode = f_control & _MCW_RC;
+		uint32_t precision_mode = f_control & _MCW_PC;
+		if(rounding_mode != _RC_NEAR) {
+			std::cerr << "Floating point rounding mode is currently '" << 
+				((rounding_mode == _RC_CHOP) ? "chop" :
+				(rounding_mode == _RC_UP) ? "up" :
+				(rounding_mode == _RC_DOWN) ? "down" :
+				(rounding_mode == _RC_NEAR) ? "near" :
+				"unknown") << "' setting to 'near'\n";
+			if(_controlfp_s(&unused, _RC_NEAR, _MCW_RC)) {
+				std::cerr << "failed to set floating point rounding type to 'near'\n";
+			}
+		}
+		if(precision_mode != _PC_53) {
+			std::cerr << "Floating point precision mode is currently '" << 
+				((precision_mode == _PC_53) ? "double" :
+				(precision_mode == _PC_24) ? "single" :
+				(precision_mode == _PC_64 ) ? "double extended" :
+				"unknown") << "' setting to 'double'\n";
+			if(_controlfp_s(&unused, _PC_53, _MCW_PC)) {
+				std::cerr << "failed to set floating point precision type to 'double'\n";
+			}
+		}
+	}
+	else {
+		std::cerr << "_controlfp_s failed.\n";
+	}
+}
+#endif
 /**
  * Setups the game environment and enters
  * the titlescreen or game loops.
@@ -573,6 +608,9 @@ static int do_gameloop(const std::vector<std::string>& args)
 		}
 	}
 
+#if defined(_WIN32)
+	check_fpu();
+#endif
 	const cursor::manager cursor_manager;
 	cursor::set(cursor::WAIT);