Move tar function headers to pgtar.h

This makes it possible to include them only where they are used, so
we can avoid the conflict of the uid_t and gid_t datatypes that happened
in plperl (since plperl doesn't need the tar functions)

src/backend/replication/basebackup.c

@@ -32,6 +32,7 @@
 #include "utils/builtins.h"
 #include "utils/elog.h"
 #include "utils/ps_status.h"
+#include "pgtar.h"
 
 typedef struct
 {

src/bin/pg_dump/pg_backup_tar.c

@@ -30,6 +30,7 @@
 #include "pg_backup_tar.h"
 #include "dumpmem.h"
 #include "dumputils.h"
+#include "pgtar.h"
 
 #include <sys/stat.h>
 #include <ctype.h>

src/include/pgtar.h

@@ -0,0 +1,15 @@
+/*-------------------------------------------------------------------------
+ *
+ * pgtar.h
+ *	  Functions for manipulating tarfile datastructures (src/port/tar.c)
+ *
+ *
+ * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/pgtar.h
+ *
+ *-------------------------------------------------------------------------
+ */
+extern void tarCreateHeader(char *h, const char *filename, const char *linktarget, size_t size, mode_t mode, uid_t uid, gid_t gid, time_t mtime);
+extern int	tarChecksum(char *header);

src/include/port.h

@@ -465,8 +465,4 @@ extern int	pg_check_dir(const char *dir);
 /* port/pgmkdirp.c */
 extern int	pg_mkdir_p(char *path, int omode);
 
-/* port/tar.c */
-void		tarCreateHeader(char *h, const char *filename, const char *linktarget, size_t size, mode_t mode, uid_t uid, gid_t gid, time_t mtime);
-int			tarChecksum(char *header);
-
 #endif   /* PG_PORT_H */

src/port/tar.c

@@ -1,4 +1,5 @@
 #include "c.h"
+#include "pgtar.h"
 #include <sys/stat.h>
 
 /*