don't use isnormal() to test for crazy FP numbers

it fails for 0.0 and for subnormal numbers, thanks Murat Korkmazov

ChangeLog

@@ -17,6 +17,7 @@
 - add VInterpolate class to cplusplus binding, thanks Lovell
 - add lower-level operation cache access
 - turn on leak testing in test suite
+- don't use isnormal() to test for crazy FP numbers, thanks Murat
 
 24/12/14 started 7.42.1
 - add gobject-2.0 to Requires: in vips and vips-cpp .pc files

libvips/colour/LabQ2sRGB.c

@@ -269,10 +269,13 @@ vips_col_scRGB2sRGB( int range, int *lut,
 
 	/* XYZ can be Nan, Inf etc. Throw those values out, they will break
 	 * our clipping.
+	 *
+	 * Don't use isnormal(), it is false for 0.0 and for subnormal
+	 * numbers. 
 	 */
-	if( !isnormal( R ) ||
-		!isnormal( G ) ||
-		!isnormal( B ) ) {
+	if( isnan( R ) || isinf( R ) ||
+		isnan( G ) || isinf( G ) ||
+		isnan( B ) || isinf( B ) ) { 
 		*r = 0; 
 		*g = 0; 
 		*b = 0;