[WIP] [Stream] Preview of pg_type changes

 Hello,

 Here I would like to expose changes to pg_type and type infrastructure 
 about streaming. Changes are as follows:
 - added new column typstreamin typestremout
 - general contract for those is for streamin same as receive (receive 
 use internal), for streamout it is (internal, <type>)
 - changes to psql help
 - and all functionality for type manipulation.

 There is no streamin/streamout methods implemented.

 If someone wants and have time, as this is WIP patch, then suggestions 
 are welcome.

 Regards,
 Radek