copydir prototype

This patch:

http://git.postgresql.org/gitweb?p=postgresql.git;a=commit;h=bb0fe9feb9fd75a6aaa960028a9f810c883b0fc4

...did not tidy up after itself as well as it might have.  In
particular, it left the prototype for copydir() in src/include/port.h,
while moving the source file from src/port/copydir.c to
src/backend/storage/file/copydir.c.  I think this should probably be
cleaned up, but I'm a little uncertain where the best place to put
that prototype is.  I am tempted to just put this in a new header file
named according to our usual conventions, namely
src/include/storage/copydir.c, but since there's only one public
function at present perhaps someone would like to argue for including
it in some other, already-exstant header.

A patch I'm working on needs to expose the copy_file() function, which
is currently static to copydir.c, so maybe it would be preferable to
rename copydir.c to copy.c and add the header as
src/include/storage/copy.h.

Thoughts?

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company