Merge pull request 2ndQuadrant#2 from 3nids/schemasafe

`text || regclass`, via the `regclass` to `text` cast, already quotes table identifiers where necessary. The `quote_ident` calls here are unnecessary, and in fact incorrect as they result in quotes that were part of the table quoting becoming part of the identifier name.

Example:

```
create table "I will
hack your');DROP TABLE student;--" (
haha integer
);

SELECT '"I will
hack your'');DROP TABLE student;--"'::regclass::oid;

-- Produces oid 53060 here

regress=> SELECT 'DROP TABLE ' || 53060::oid::regclass;
              ?column?              
------------------------------------
 DROP TABLE "I will                +
 hack your');DROP TABLE student;--"
(1 row)

regress=> SELECT 'DROP TABLE ' || quote_ident(53060::oid::regclass::text);
               ?column?               
--------------------------------------
 DROP TABLE """I will                +
 hack your');DROP TABLE student;--"""
(1 row)
```

audit.sql

@@ -184,15 +184,15 @@ DECLARE
   _q_txt text;
   _ignored_cols_snip text = '';
 BEGIN
-    EXECUTE 'DROP TRIGGER IF EXISTS audit_trigger_row ON ' || quote_ident(target_table::text);
-    EXECUTE 'DROP TRIGGER IF EXISTS audit_trigger_stm ON ' || quote_ident(target_table::text);
+    EXECUTE 'DROP TRIGGER IF EXISTS audit_trigger_row ON ' || target_table;
+    EXECUTE 'DROP TRIGGER IF EXISTS audit_trigger_stm ON ' || target_table;
 
     IF audit_rows THEN
         IF array_length(ignored_cols,1) > 0 THEN
             _ignored_cols_snip = ', ' || quote_literal(ignored_cols);
         END IF;
         _q_txt = 'CREATE TRIGGER audit_trigger_row AFTER INSERT OR UPDATE OR DELETE ON ' || 
-                 quote_ident(target_table::text) || 
+                 target_table || 
                  ' FOR EACH ROW EXECUTE PROCEDURE audit.if_modified_func(' ||
                  quote_literal(audit_query_text) || _ignored_cols_snip || ');';
         RAISE NOTICE '%',_q_txt;
@@ -202,7 +202,7 @@ BEGIN
     END IF;
 
     _q_txt = 'CREATE TRIGGER audit_trigger_stm AFTER ' || stm_targets || ' ON ' ||
-             quote_ident(target_table::text) ||
+             target_table ||
              ' FOR EACH STATEMENT EXECUTE PROCEDURE audit.if_modified_func('||
              quote_literal(audit_query_text) || ');';
     RAISE NOTICE '%',_q_txt;