fix worldsave when backup files are present

When backup files from other tools are present in the region folder
Minutor could hang infinitely while trying to calculate the world
border. This commit completely rewrites the Chunk number from region
file detection code.
This commit closes #60

worldsave.cpp

@@ -224,27 +224,39 @@ void WorldSave::findBounds(QString path, int *top, int *left, int *bottom, int *
 	//loop through all region files and find the extremes
 	while (it.hasNext())
 	{
-		QString fn=it.next();
-		int pos=fn.length()-5;
-		ushort c;
-		//figure out the x/z of the region
-		for (int i=0;i<2;i++)
+		it.next();
+		QString fn=it.fileName();
+		int len=fn.length()-4; // length of filename
+
+		//figure out the X of the region
+		int posX=2; // position after "r."
+		int posE=posX;
+		while ( posE<len && 
+				( fn.at(posE)=='+' ||
+				  fn.at(posE)=='-' ||
+				  fn.at(posE).isDigit()
+				)
+		      )
 		{
-			int p=0;
-			int scale=1;
-			while (pos>0 && (c=fn.at(pos).unicode())!='.')
-			{
-				if (c=='-')
-					p=-p;
-				else
-					p+=(c-'0')*scale;
-				pos--;
-				scale*=10;
-			}
-			pos--;
-			if (i==0) cur.z=p;
-			else cur.x=p;
+			posE++;
 		}
+        QStringRef numX(&fn, posX, posE-posX);
+		cur.x = numX.toInt();
+
+		//figure out the Z of the region
+		int posZ=++posE;
+		while ( posE<len && 
+				( fn.at(posE)=='+' ||
+				  fn.at(posE)=='-' ||
+				  fn.at(posE).isDigit()
+				)
+		      )
+		{
+			posE++;
+		}
+        QStringRef numZ(&fn, posZ, posE-posZ);
+		cur.z = numZ.toInt();
+
 		if (!hasOne)
 		{
 			for (int e=0;e<4;e++)