[ADD] tools: add escape_psql function

By default, Odoo support _ and % in domain to search like in pgsql.
But if you want to search something starting by _ or containing %
the developper need to escape these character.

openerp/tools/sql.py

@@ -4,3 +4,6 @@
 def drop_view_if_exists(cr, viewname):
     cr.execute("DROP view IF EXISTS %s CASCADE" % (viewname,))
     cr.commit()
+
+def escape_psql(to_escape):
+    return to_escape.replace('\\', r'\\').replace('%', '\%').replace('_', '\_')