mesh-rasterize: Fix number of iterations

Commit 44a09f462c fixed a compiler warning, but changed the result of this code.
This is because the old 'for' loop did one more iteration than the new 'while'
loop. Fix this by incrementing the loop counter once before the loop.

Fixes: mesh-pattern mesh-pattern-accuracy mesh-pattern-conical
mesh-pattern-control-points mesh-pattern-fold mesh-pattern-overlap
mesh-pattern-transformed record-mesh

Signed-off-by: Uli Schlachter <psychon@znc.in>
Tested-by: Bryce Harrington <b.harrington@samsung.com>

src/cairo-mesh-pattern-rasterizer.c

@@ -728,6 +728,7 @@ rasterize_bezier_patch (unsigned char *data, int width, int height, int stride,
 	dcend[i]   = (col[3][i] - col[1][i]) / v;
     }
 
+    v++;
     while (v--) {
 	cairo_point_double_t nodes[4];
 	for (i = 0; i < 4; ++i) {