[Bug ada/124143] implement AI12-0331 binding interpretation

[liam at liampwll dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124143

--- Comment #6 from Liam Powell <liam at liampwll dot com> ---
s/Put_Line ("null");/Put ("null");

after:

if Subpool.Node = null or else Subpool.Node.Owner = null then