better matrix header read

TODO

@@ -1,15 +1,3 @@
-- try:
-
-	john@kiwi:~/pics$ more sharp3x3.mat 
-	3 3
-	-1 -1 -1
-	-1 8 -1
-	-1 -1 -1
-	john@kiwi:~/pics$ vips convi k2.jpg x.jpg sharp3x3.con
-	VipsForeignLoad: file "sharp3x3.con" not found
-
-  works if you add 1 0 to the header line
-
 - not sure about utf8 error messages on win
 
 - strange: 

libvips/foreign/csv.c

@@ -31,7 +31,7 @@
  * 	- try to support DOS files under linux ... we have to look for \r\n
  * 	  linebreaks
  * 12/8/16
- * 	- allow missing offset in matrix header
+ * 	- allow missing offset and scale in matrix header
  */
 
 /*
@@ -488,7 +488,7 @@ fetch_nonwhite( FILE *fp, const char whitemap[256], char *buf, int max )
 
 /* Read a single double in ascii (not locale) encoding.
  *
- * Return the char that caused failure on fail (EOF or \n).
+ * Return the char that caused failure on fail (EOF or \n). 
  */
 static int
 read_ascii_double( FILE *fp, const char whitemap[256], double *out )
@@ -536,20 +536,19 @@ vips__matrix_header( char *whitemap, FILE *fp,
 	int i;
 	int ch;
 
-	/* Offset defaults to zero.
-	 */
-	header[2] = 1.0;
-	header[3] = 0.0;
-
 	for( i = 0; i < 4 && 
 		(ch = read_ascii_double( fp, whitemap, &header[i] )) == 0; 
 		i++ )
 		;
-
+	if( i < 4 )
+		header[3] = 0.0;
+	if( i < 3 )
+		header[2] = 1.0;
 	if( i < 2 ) {
 		vips_error( "mask2vips", "%s", _( "no width / height" ) );
 		return( -1 );
 	}
+
 	if( VIPS_FLOOR( header[0] ) != header[0] ||
 		VIPS_FLOOR( header[1] ) != header[1] ) {
 		vips_error( "mask2vips", "%s", _( "width / height not int" ) );

libvips/foreign/matrixload.c

@@ -181,7 +181,7 @@ vips_foreign_load_matrix_init( VipsForeignLoadMatrix *matrix )
  * floating-point, and must use '.'
  * as a decimal separator.
  *
- * Subsequent lines each hold one line of matrix data, with numbers again
+ * Subsequent lines each hold one row of matrix data, with numbers again
  * separated by any mixture of spaces, commas, 
  * tabs and quotation marks ("). The numbers may be floating-point, and must
  * use '.'