plproxy - plproxy: Avoid parsing "SELECT (" as function call Currently

Log Message:
-----------
Avoid parsing "SELECT (" as function call

Currently PL/Proxy fails to parse following statement:

  select (0*0);

As only SELECT statement is affected, fix it by explicitly checking
for that case.

In long-term, the function-call detection should be moved to parser,
thus getting rid of the hack.

Patch by Peter Eisentraut

Modified Files:
--------------
    plproxy/expected:
        plproxy_select.out (r1.2 -> r1.3)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plproxy/plproxy/expected/plproxy_select.out?r1=1.2&r2=1.3)
    plproxy/sql:
        plproxy_select.sql (r1.1.1.1 -> r1.2)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plproxy/plproxy/sql/plproxy_select.sql?r1=1.1.1.1&r2=1.2)
    plproxy/src:
        scanner.l (r1.13 -> r1.14)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plproxy/plproxy/src/scanner.l?r1=1.13&r2=1.14)