fix a compile fail if no libtiff

compilation failed if libtiff-dev was not found, thanks Martin

ChangeLog

@@ -1,5 +1,6 @@
 13/9/12 started 7.30.3
 - linecache sized itself too large
+- fix a compile failure if libtiff was not found (thanks Martin)
 
 4/9/12 started 7.30.2
 - sequential stops all threads on error

libvips/deprecated/im_tiff2vips.c

@@ -83,6 +83,7 @@ tiff2vips( const char *name, IMAGE *out, gboolean header_only )
 	 * malloc if all we are doing is looking at fields.
 	 */
 
+#ifdef HAVE_TIFF
 	if( !header_only &&
 		!seq &&
 		!vips__istifftiled( filename ) &&
@@ -91,7 +92,6 @@ tiff2vips( const char *name, IMAGE *out, gboolean header_only )
 			return( -1 );
 	}
 
-#ifdef HAVE_TIFF
 	if( header_only ) {
 		if( vips__tiff_read_header( filename, out, page ) )
 			return( -1 );