PL1 — Remove Errors and Ambiguities from Code Examples in PL/I Mapping Specificat

(Note that the page numbers are those used by the PDF document, which
says that there are 106 pages in all for this doc)

PAGE 24 - the line:
=======
3 d fixed bin(31),
should be:
3 d fixed bin(31) init(0),

PAGE 25 - missing line:
=======
after the line:
do;
insert:
example_user_exceptions.d=1; /* 1=example_bad, 2=example_worse */

PAGE 26 correction:
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The 'if', 'select' and 'when' statements were incorrect - what was in the
document before was ambiguous. The first part (down to the second 'when'
statement in the code on page 26 should be replaced with the following
(same as before with the if/select/when amendments):

CHECK_ERRORS: PROC(FUNCTION_NAME) RETURNS(FIXED BIN(31));
dcl exc_name char(64);
dcl exception_info char(64);

if example_user_exception.d ^= 0 then
do;
display('example_user_exception');
strget(exception_id,64,exc_name);
select(example_user_exception.d);
when(1)
do;
display('value1 =' ||example_bad.value1);
display('reason =' ||example_bad.reason);
end;
when(2)
... (as before in the document) ...

PAGE 106 - code example mistake - as in page 26 above
========
The same happens on page 106 (the formatting of the code on the page also
needs some tidying as far as format is concerned). On this page, the 'if'
down to the second 'when' statement needs to be replaced with the 'if'
block shown above.

PAGE 31
=======
All the lines of code which say:
if vtptr=sysnull() || p_vtargs=null

should be replaced with:
if vtptr=sysnull() || p_vtargs=sysnull()

PAGE 33
=======
Amend the line:
3 ctl ptr,
to be:
3 ctl ptr init(sysnull()),

resolved