pgsql: Move copydir() prototype into its own header file.

Move copydir() prototype into its own header file.

Having this in src/include/port.h makes no sense, now that copydir.c lives
in src/backend/strorage rather than src/port. Along the way, remove an
obsolete comment from contrib/pg_upgrade that makes reference to the old
location.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=11e482c350c431fb2f51c6ceb847e5e31ea38911

Modified Files
--------------
contrib/pg_upgrade/pg_upgrade.c | 1 -
src/backend/commands/dbcommands.c | 1 +
src/backend/storage/file/copydir.c | 1 +
src/include/port.h | 2 --
src/include/storage/copydir.h | 18 ++++++++++++++++++
5 files changed, 20 insertions(+), 3 deletions(-)