Allows picture.datatype to be used as an image.

This patch allows application to use a picture.datatype 
(subclass) object like an image using the DTM_OBTAINDRAWINFO,
DTM_DRAW and DTM_RELEASEDRAWINFO methods (and the matching
datatypes.library functions ObtainDTDrawInfoA, DrawDTObjectA,
ReleaseDTDrawInfo as documented in V45); this interface
replaces the ugly direct bitmap access.

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                 2727    4480  60.9% -lh5- 867d Apr 25  1997 drawablepicdtc/drawablepicdtc
[generic]                 6941   25505  27.2% -lh5- b89d Apr 25  1997 drawablepicdtc/drawablepicdtc.c
[generic]                  256     486  52.7% -lh5- be27 Apr 25  1997 drawablepicdtc/drawablepicdtc.c.info
[generic]                 1549    3205  48.3% -lh5- 07a2 Apr 25  1997 drawablepicdtc/drawablepicdtc.doc
[generic]                  387     835  46.3% -lh5- ce82 Apr 25  1997 drawablepicdtc/drawablepicdtc.info
[generic]                 4524    7932  57.0% -lh5- 320d Apr 25  1997 drawablepicdtc/drawablepicdtc.ld
[generic]                  117     201  58.2% -lh5- 92d7 Apr 25  1997 drawablepicdtc/drawablepicdtc_rev.h
[generic]                  130     243  53.5% -lh5- 3b55 Apr 25  1997 drawablepicdtc/drawablepicdtc_rev.i
[generic]                    2       2 100.0% -lh0- 9795 Apr 25  1997 drawablepicdtc/drawablepicdtc_rev.rev
[generic]                  983    3731  26.3% -lh5- bb30 Apr 25  1997 drawablepicdtc/SMakefile
[generic]                  255     486  52.5% -lh5- 6a7e Apr 25  1997 drawablepicdtc/SMakefile.info
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total        11 files   17871   47106  37.9%            Apr 29  1997