setstdin

[Jeff Horwitz]

i just wrote a custom mod_parrot filehandle PMC that sends output back to 
the Apache client.  i can assign it to stdout using the setstdout opcode 
and all "prints" and "says" are magically sent back to the client.  this 
required for registry-style scripts and PHP.

i need to do the same for stdin for reading POST data, but i just noticed 
that setstdin is missing.  thoughts on adding it?

-jeff