#628 help message wrong for structures arrays

[giloo]

GDL> toto=replicate(!D,32)
GDL> help,toto
** Structure !DEVICE, 17 tags, data length=272:
NAME STRING 'X'
X_SIZE LONG 640
Y_SIZE LONG 512
(etc)

IDL> toto=replicate(!D,32)
IDL> help,toto
TOTO STRUCT = -> !DEVICE Array[32]
IDL> help,toto,/str
** Structure !DEVICE, 17 tags, length=88, data length=88:
NAME STRING 'X'
X_SIZE LONG 640
Y_SIZE LONG 512

(etc)

[GregJung]

272 indicates this GDL version is aligning entries on 16-byte boundaries.(17 * 16=272). Two of the tags are lonarr(2) so in
IDL the non-string storage = 14 * 4+16=72 and string is kept in
a 16-byte slot.

GDL> str4={ x: 0l, y: lonarr(2), z: 0, aa: 0, bb:0, cc:0}
GDL> help,/st,str4
** Structure <Anonymous>, 6 tags, data length=96:
   X               LONG                 0
   Y               LONG      Array[2]
   Z               INT              0
   AA              INT              0
   BB              INT              0
   CC              INT              0
GDL> print,16*6
      96

The "data length=" refers to what is allocated in GDL itself,
probably par->Sizeof() where par->NBytes() is conformant if NBytes is re-defined (post 0.9.5) to be the actual data occupancy rather than Sizeof(). This appears again in the /F77_unformatted mode of writeu and readu which is wrong in versions 0.x thru 0.9.5; when NBytes() is made to count the actual storage, it is corrected.

[Sylwester Arabas]

moved to github: https://github.com/gnudatalanguage/gdl/issues/181