Allows marking in text.datatype and subclasses.
This update is more directory.datatype friendly.

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                 2681    4184  64.1% -lh5- b788 Sep 27  1996 markabletextdtclass/markabletextdtclass
[generic]                 3905   15803  24.7% -lh5- 8444 Sep 27  1996 markabletextdtclass/markabletextdtclass.c
[generic]                  251     486  51.6% -lh5- 4287 Aug 25  1996 markabletextdtclass/markabletextdtclass.c.info
[generic]                 1834    4515  40.6% -lh5- 1881 Sep 27  1996 markabletextdtclass/markabletextdtclass.guide
[generic]                  253     486  52.1% -lh5- 6be1 Aug 26  1996 markabletextdtclass/markabletextdtclass.guide.info
[generic]                  392     835  46.9% -lh5- b0e8 Aug 25  1996 markabletextdtclass/markabletextdtclass.info
[generic]                 4696    9352  50.2% -lh5- 3356 Sep 27  1996 markabletextdtclass/markabletextdtclass.ld
[generic]                  122     216  56.5% -lh5- 92ff Aug 25  1996 markabletextdtclass/markabletextdtclass_rev.h
[generic]                  134     258  51.9% -lh5- 3bac Aug 25  1996 markabletextdtclass/markabletextdtclass_rev.i
[generic]                    2       2 100.0% -lh0- 9795 Aug 25  1996 markabletextdtclass/markabletextdtclass_rev.rev
[generic]                  997    3839  26.0% -lh5- 4c44 Aug 26  1996 markabletextdtclass/SMakefile
[generic]                  253     486  52.1% -lh5- 8558 May 18  1996 markabletextdtclass/SMakefile.info
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total        12 files   15520   40462  38.4%            Oct 20  1996