ECPG support for struct in INTO list

Hi,

one of our clients wants to port their application suite
from Informix to PostgreSQL, they use constructs like

SELECT * INTO :tablerec FROM table ...

where "tablerec" mirrors the table fields in a C struct.

Currently ECPG dumps core on this, more exactly aborts on it
in ecpg_type_name().

Patch is attached that solves it by introducing add_struct_to_head()
called from rule "coutputvariable" that also catches C unions now,
emitting an error because unions cannot be unambiguously unrolled.
It tries to handle NULL indicator, expecting a struct with at least
the same amount of members.

Best regards,
Zoltán Böszörményi

--
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Zoltán Böszörményi
Cybertec Schönig & Schönig GmbH
http://www.postgresql.at/