small spi patch

Hi,

This is small patch fixes a spi example (PG_MODULE_MAGIC is required as
of PostgreSQL 8.2) and provides a link to compiling and linking section.


--
  Euler Taveira de Oliveira
  http://www.timbira.com/
*** spi.sgml.orig    2007-08-23 23:57:09.000000000 -0300
--- spi.sgml    2007-08-24 00:06:37.000000000 -0300
***************
*** 3325,3330 ****
--- 3325,3334 ----
  <programlisting>
  #include "executor/spi.h"

+ #ifdef PG_MODULE_MAGIC
+ PG_MODULE_MAGIC;
+ #endif
+
  int execq(text *sql, int cnt);

  int
***************
*** 3380,3386 ****

    <para>
     This is how you declare the function after having compiled it into
!    a shared library:

  <programlisting>
  CREATE FUNCTION execq(text, integer) RETURNS integer
--- 3384,3390 ----

    <para>
     This is how you declare the function after having compiled it into
!    a shared library (details are in <xref linkend="dfunc">.):

  <programlisting>
  CREATE FUNCTION execq(text, integer) RETURNS integer