Pg: Add "$hex" pseudo-type

FU/Pg.pm

@@ -619,7 +619,21 @@ supported. C<undef> always converts to SQL C<NULL>.
 =item bytea
 
 The C<bytea> type represents arbitrary binary data and this module will pass
-that along as raw binary strings.
+that along as raw binary strings. If you prefer to work with hex strings
+instead, use:
+
+  $conn->set_type(bytea => '$hex');
+
+The I<bytea> and the I<$hex> (pseudo-)types can be applied to any other type to
+convert between the PostgreSQL binary wire format and Perl strings. For
+example, if you prefer to receive integers as big-endian hex strings, you can
+do that:
+
+  $conn->set_type(int4 => recv => '$hex');
+
+Or to treat UUIDs as 16-byte strings:
+
+  $conn->set_type(uuid => 'bytea');
 
 =item timestamp / timestamptz
 
@@ -724,8 +738,6 @@ C<set_type()> to configure appropriate conversions for these types.
 
 =back
 
-I<TODO:> Some handy special types for overriding common conversions.
-
 I<TODO:> Methods to convert between the various formats.
 
 I<TODO:> Methods to query type info.