pgsql: kill() is declared in <signal.h> per Single Unix Spec.

Log Message:
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kill() is declared in <signal.h> per Single Unix Spec.

Modified Files:
--------------
pgsql/src/test/regress:
pg_regress.c (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/pg_regress.c.diff?r1=1.2&amp;r2=1.3)