prefix - prefix: add indexing lookup support for <@, = and &&

Log Message:
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add indexing lookup support for <@, = and &&

Modified Files:
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prefix:
prefix.c (r1.47 -> r1.48)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/prefix/prefix/prefix.c?r1=1.47&amp;r2=1.48)
prefix.sql.in (r1.25 -> r1.26)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/prefix/prefix/prefix.sql.in?r1=1.25&amp;r2=1.26)