Use the spec-mandated default YCbCrSubSampling values in strip size
calculations, if the YCBCRSUBSAMPLING tag hasn't been provided.
See bug #603703.

Filed upstream at http://bugzilla.maptools.org/show_bug.cgi?id=2215

diff -Naurp tiff-3.9.1/libtiff/tif_strip.c tiff-3.9.1.oden/libtiff/tif_strip.c
--- tiff-3.9.1/libtiff/tif_strip.c	2006-03-25 13:04:35.000000000 -0500
+++ tiff-3.9.1.oden/libtiff/tif_strip.c	2010-08-05 10:51:52.000000000 -0400
@@ -124,9 +124,9 @@ TIFFVStripSize(TIFF* tif, uint32 nrows)
 		uint16 ycbcrsubsampling[2];
 		tsize_t w, scanline, samplingarea;
 
-		TIFFGetField( tif, TIFFTAG_YCBCRSUBSAMPLING,
-			      ycbcrsubsampling + 0,
-			      ycbcrsubsampling + 1 );
+		TIFFGetFieldDefaulted(tif, TIFFTAG_YCBCRSUBSAMPLING,
+				      ycbcrsubsampling + 0,
+				      ycbcrsubsampling + 1);
 
 		samplingarea = ycbcrsubsampling[0]*ycbcrsubsampling[1];
 		if (samplingarea == 0) {
@@ -234,9 +234,9 @@ TIFFScanlineSize(TIFF* tif)
 		    && !isUpSampled(tif)) {
 			uint16 ycbcrsubsampling[2];
 
-			TIFFGetField(tif, TIFFTAG_YCBCRSUBSAMPLING,
-				     ycbcrsubsampling + 0,
-				     ycbcrsubsampling + 1);
+			TIFFGetFieldDefaulted(tif, TIFFTAG_YCBCRSUBSAMPLING,
+					      ycbcrsubsampling + 0,
+					      ycbcrsubsampling + 1);
 
 			if (ycbcrsubsampling[0] == 0) {
 				TIFFErrorExt(tif->tif_clientdata, tif->tif_name,
@@ -308,9 +308,9 @@ TIFFNewScanlineSize(TIFF* tif)
 		    && !isUpSampled(tif)) {
 			uint16 ycbcrsubsampling[2];
 
-			TIFFGetField(tif, TIFFTAG_YCBCRSUBSAMPLING,
-				     ycbcrsubsampling + 0,
-				     ycbcrsubsampling + 1);
+			TIFFGetFieldDefaulted(tif, TIFFTAG_YCBCRSUBSAMPLING,
+					      ycbcrsubsampling + 0,
+					      ycbcrsubsampling + 1);
 
 			if (ycbcrsubsampling[0]*ycbcrsubsampling[1] == 0) {
 				TIFFErrorExt(tif->tif_clientdata, tif->tif_name,