[ODBC] more bugs with returning 0 for malloc(0)

Hello, psqlODBC team.

I'm reporting a bug.
This simular to the following bug.

https://git.postgresql.org/gitweb/?p=psqlodbc.git;a=commit;h=ae12eef5ccb754d1cd9a4f12e8e88e56e0497bc2

Some codes consider it error when zero size malloc/calloc return NULL.
I think we should add zero size check codes there.

columninfo.c: CI_read_fields_from_pgres(), CI_set_num_fkields()
convert.c: QB_initialize_copy()
bind.c:    create_empty_bindings()
bind.c:    create_empty_gdata()

Unexpected SQL execution failures reported on AIX with the latest psqlodbc.

mylog:
[1]about to begin SC_execute
[1]libpq_bind_and_exec: bind stmt=2008e3c8
[1]STATEMENT ERROR: func=SC_execute, desc='', errnum=34, errmsg='Could not receive the response, communication down ??'
[1]CONN ERROR: func=SC_execute, desc='', errnum=0, errmsg='(NULL)'
[1]CC_on_abort in opt=2


best regards,
Haruka Takatsuka / SRA OSS, Inc. http://www.sraoss.co.jp