psqlodbc - psqlodbc: Clear col_info(columns info) cache ehen DROP/ALTER

Log Message:
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Clear col_info(columns info) cache ehen DROP/ALTER TABLE is called
so that later SQLDescribeCol() etc work properly.

Modified Files:
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psqlodbc:
connection.c (r1.195 -> r1.196)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/psqlodbc/psqlodbc/connection.c?r1=1.195&r2=1.196)