Fix bufferDrawLine

Missing 1 pixel in the middle of the vertical line.

src/draw.cc

@@ -27,7 +27,7 @@ void bufferDrawLine(unsigned char* buf, int pitch, int x1, int y1, int x2, int y
 
         p1 = buf + pitch * y1 + x1;
         p2 = buf + pitch * y2 + x2;
-        while (p1 < p2) {
+        while (p1 <= p2) {
             *p1 = color;
             *p2 = color;
             p1 += pitch;