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.

contrib/pg_upgrade/pg_upgrade.c

@@ -259,7 +259,6 @@ copy_clog_xlog_xid(void)
 	check_ok();
 
 	prep_status("Copying old commit clogs to new server");
-	/* libpgport's copydir() doesn't work in FRONTEND code */
 #ifndef WIN32
 	exec_prog(true, SYSTEMQUOTE "%s \"%s\" \"%s\"" SYSTEMQUOTE,
 			  "cp -Rf",

src/backend/commands/dbcommands.c

@@ -44,6 +44,7 @@
 #include "pgstat.h"
 #include "postmaster/bgwriter.h"
 #include "storage/bufmgr.h"
+#include "storage/copydir.h"
 #include "storage/fd.h"
 #include "storage/lmgr.h"
 #include "storage/ipc.h"

src/backend/storage/file/copydir.c

@@ -22,6 +22,7 @@
 #include <unistd.h>
 #include <sys/stat.h>
 
+#include "storage/copydir.h"
 #include "storage/fd.h"
 #include "miscadmin.h"
 

src/include/port.h

@@ -288,8 +288,6 @@ extern int	pgsymlink(const char *oldpath, const char *newpath);
 #define symlink(oldpath, newpath)	pgsymlink(oldpath, newpath)
 #endif
 
-extern void copydir(char *fromdir, char *todir, bool recurse);
-
 extern bool rmtree(const char *path, bool rmtopdir);
 
 /*

src/include/storage/copydir.h

@@ -0,0 +1,18 @@
+/*-------------------------------------------------------------------------
+ *
+ * port.h
+ *	  Header for src/port/ compatibility functions.
+ *
+ * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/port.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef COPYDIR_H
+#define COPYDIR_H
+
+extern void copydir(char *fromdir, char *todir, bool recurse);
+
+#endif   /* COPYDIR_H */