Fix misbehavior on 64-bit machines when trying to flip a downsampled image

vertically: unsigned ints will be widened to 64 bits the wrong way.

See RH bug #583081.

Filed upstream at http://bugzilla.maptools.org/show_bug.cgi?id=2207

diff -Naur tiff-3.9.2.orig/libtiff/tif_getimage.c tiff-3.9.2/libtiff/tif_getimage.c

--- tiff-3.9.2.orig/libtiff/tif_getimage.c	2009-08-30 12:21:46.000000000 -0400

+++ tiff-3.9.2/libtiff/tif_getimage.c	2010-06-10 15:07:28.000000000 -0400

@@ -1846,6 +1846,7 @@

 DECLAREContigPutFunc(putcontig8bitYCbCr22tile)

 {

 	uint32* cp2;

+	int32 incr = 2*toskew+w;

 	(void) y;

 	fromskew = (fromskew / 2) * 6;

 	cp2 = cp+w+toskew;

@@ -1872,8 +1873,8 @@

 			cp2 ++ ;

 			pp += 6;

 		}

-		cp += toskew*2+w;

-		cp2 += toskew*2+w;

+		cp += incr;

+		cp2 += incr;

 		pp += fromskew;

 		h-=2;

 	}

@@ -1939,6 +1940,7 @@

 DECLAREContigPutFunc(putcontig8bitYCbCr12tile)

 {

 	uint32* cp2;

+	int32 incr = 2*toskew+w;

 	(void) y;

 	fromskew = (fromskew / 2) * 4;

 	cp2 = cp+w+toskew;

@@ -1953,8 +1955,8 @@

 			cp2 ++;

 			pp += 4;

 		} while (--x);

-		cp += toskew*2+w;

-		cp2 += toskew*2+w;

+		cp += incr;

+		cp2 += incr;

 		pp += fromskew;

 		h-=2;

 	}