DATAMATRIX: add DM_ISO_144 (--dmiso144) option for ISO placement

of ECC codewords instead of default "de facto"

docs/manual.txt

@@ -3150,7 +3150,7 @@ check digit.
 A highly compressed symbol for numeric data. The number of channels in the
 symbol can be between 3 and 8 and this can be specified by setting the value of
 the --vers option (API option_2). It can also be determined by the length of the
-input data e.g. a three character input string generates a 4 channel code by
+input data: e.g. a three character input string generates a 4 channel code by
 default.
 
 The maximum values permitted depend on the number of channels used as shown in
@@ -3721,6 +3721,10 @@ GS1 data may be encoded using FNC1 (default) or GS (Group Separator, ASCII 29)
 as separator. Use the option --gssep to change to GS (API
 output_options |= GS1_GS_SEPARATOR).
 
+By default Zint uses a “de facto” codeword placement for symbols of size 144 x
+144 (version 24). To override this and use the now clarified ISO/IEC standard
+placement, use option --dmiso144 (API option_3 |= DM_ISO_144).
+
 For a faster but less optimal encoding, the --fast option (API
 input_mode |= FAST_MODE) may be used.
 
@@ -4842,10 +4846,16 @@ OPTIONS
     Send output to stdout, which in most cases should be re-directed to a pipe
     or a file. Use --filetype to specify output format.
 
+--dmiso144
+
+    For Data Matrix symbols, use the standard ISO/IEC codeword placement for 144
+    x 144 (--vers=24) sized symbols, instead of the default “de facto” placement
+    (which rotates the placement of ECC codewords).
+
 --dmre
 
     For Data Matrix symbols, allow Data Matrix Rectangular Extended (DMRE) sizes
-    when considering automatic sizes.
+    when considering automatic sizes. See also --square.
 
 --dotsize=NUMBER
 
@@ -5122,7 +5132,7 @@ OPTIONS
 --square
 
     For Data Matrix symbols, exclude rectangular sizes when considering
-    automatic sizes.
+    automatic sizes. See also --dmre.
 
 --structapp=I,C[,ID]