Documentation fix for ALTER TYPE .. RENAME

The documentation for ALTER TYPE .. RENAME claimed to support a
RESTRICT/CASCADE option at the 'type' level, which wasn't implemented
and doesn't make a whole lot of sense to begin with.  What is supported,
and previously undocumented, is

ALTER TYPE .. RENAME ATTRIBUTE .. RESTRICT/CASCADE.

I've updated the documentation and back-patched this to 9.1 where it was
first introduced.

doc/src/sgml/ref/alter_type.sgml

@@ -25,8 +25,8 @@ PostgreSQL documentation
 <synopsis>
 ALTER TYPE <replaceable class="PARAMETER">name</replaceable> <replaceable class="PARAMETER">action</replaceable> [, ... ]
 ALTER TYPE <replaceable class="PARAMETER">name</replaceable> OWNER TO <replaceable class="PARAMETER">new_owner</replaceable>
-ALTER TYPE <replaceable class="PARAMETER">name</replaceable> RENAME ATTRIBUTE <replaceable class="PARAMETER">attribute_name</replaceable> TO <replaceable class="PARAMETER">new_attribute_name</replaceable>
-ALTER TYPE <replaceable class="PARAMETER">name</replaceable> RENAME TO <replaceable class="PARAMETER">new_name</replaceable> [ CASCADE | RESTRICT ]
+ALTER TYPE <replaceable class="PARAMETER">name</replaceable> RENAME ATTRIBUTE <replaceable class="PARAMETER">attribute_name</replaceable> TO <replaceable class="PARAMETER">new_attribute_name</replaceable> [ CASCADE | RESTRICT ]
+ALTER TYPE <replaceable class="PARAMETER">name</replaceable> RENAME TO <replaceable class="PARAMETER">new_name</replaceable>
 ALTER TYPE <replaceable class="PARAMETER">name</replaceable> SET SCHEMA <replaceable class="PARAMETER">new_schema</replaceable>
 ALTER TYPE <replaceable class="PARAMETER">name</replaceable> ADD VALUE [ IF NOT EXISTS ] <replaceable class="PARAMETER">new_enum_value</replaceable> [ { BEFORE | AFTER } <replaceable class="PARAMETER">existing_enum_value</replaceable> ]