Code modernization: src/m* (part 2)

* empty function
* default constructor/destructor
* remove unused Map::emergeSector(a,b)
* for range-based loops
* migrate a dirs[7] table to direction tables
* remove various old unused function

src/util/directiontables.cpp

@@ -30,6 +30,17 @@ const v3s16 g_6dirs[6] =
 	v3s16(-1, 0, 0) // left
 };
 
+const v3s16 g_7dirs[7] =
+{
+	v3s16(0,0,1), // back
+	v3s16(0,1,0), // top
+	v3s16(1,0,0), // right
+	v3s16(0,0,-1), // front
+	v3s16(0,-1,0), // bottom
+	v3s16(-1,0,0), // left
+	v3s16(0,0,0), // self
+};
+
 const v3s16 g_26dirs[26] =
 {
 	// +right, +top, +back