doc: Put callouts in SQL comments

This makes copy-and-pasting the SQL code easier.

From: Thomas Munro <thomas.munro@enterprisedb.com>

doc/src/sgml/plpgsql.sgml

@@ -5328,14 +5328,14 @@ SELECT * FROM cs_parse_url('http://foobar.com/query.cgi?baz');
 <programlisting>
 CREATE OR REPLACE PROCEDURE cs_create_job(v_job_id IN INTEGER) IS
     a_running_job_count INTEGER;
-    PRAGMA AUTONOMOUS_TRANSACTION;<co id="co.plpgsql-porting-pragma">
+    PRAGMA AUTONOMOUS_TRANSACTION; -- <co id="co.plpgsql-porting-pragma">
 BEGIN
-    LOCK TABLE cs_jobs IN EXCLUSIVE MODE;<co id="co.plpgsql-porting-locktable">
+    LOCK TABLE cs_jobs IN EXCLUSIVE MODE; -- <co id="co.plpgsql-porting-locktable">
 
     SELECT count(*) INTO a_running_job_count FROM cs_jobs WHERE end_stamp IS NULL;
 
     IF a_running_job_count &gt; 0 THEN
-        COMMIT; -- free lock<co id="co.plpgsql-porting-commit">
+        COMMIT; -- free lock <co id="co.plpgsql-porting-commit">
         raise_application_error(-20000,
                  'Unable to create a new job: a job is currently running.');
     END IF;
@@ -5402,7 +5402,7 @@ BEGIN
     SELECT count(*) INTO a_running_job_count FROM cs_jobs WHERE end_stamp IS NULL;
 
     IF a_running_job_count &gt; 0 THEN
-        RAISE EXCEPTION 'Unable to create a new job: a job is currently running';<co id="co.plpgsql-porting-raise">
+        RAISE EXCEPTION 'Unable to create a new job: a job is currently running'; -- <co id="co.plpgsql-porting-raise">
     END IF;
 
     DELETE FROM cs_active_job;
@@ -5411,7 +5411,7 @@ BEGIN
     BEGIN
         INSERT INTO cs_jobs (job_id, start_stamp) VALUES (v_job_id, now());
     EXCEPTION
-        WHEN unique_violation THEN <co id="co.plpgsql-porting-exception">
+        WHEN unique_violation THEN -- <co id="co.plpgsql-porting-exception">
             -- don't worry if it already exists
     END;
 END;

doc/src/sgml/query.sgml

@@ -754,7 +754,7 @@ SELECT city, max(temp_lo)
 <programlisting>
 SELECT city, max(temp_lo)
     FROM weather
-    WHERE city LIKE 'S%'<co id="co.tutorial-agg-like">
+    WHERE city LIKE 'S%'            -- <co id="co.tutorial-agg-like">
     GROUP BY city
     HAVING max(temp_lo) &lt; 40;
 </programlisting>