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

src/test/regress/pg_regress.c

@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/test/regress/pg_regress.c,v 1.2 2006/07/19 04:50:57 tgl Exp $
+ * $PostgreSQL: pgsql/src/test/regress/pg_regress.c,v 1.3 2006/07/19 05:21:57 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,7 @@
 #include <ctype.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
+#include <signal.h>
 #include <unistd.h>
 
 #include "getopt_long.h"