Unify some tar functionality across different parts
Move some of the tar functionality that existed mostly duplicated in both pg_dump and the walsender basebackup functionality into port/tar.c instead, so it can be used from both. It will also be used by pg_basebackup in the future, which would've caused a third copy of it around.
This seems to have broken plperl builds on Windows. Not sure what the fix is.
It seems if plperl exists it does *not* have the uid_t and gid_t datatypes? port.h has this:
/*
* Supplement to <sys/types.h>.
*
* Perl already has typedefs for uid_t and gid_t.
*/
#ifndef PLPERL_HAVE_UID_GID
typedef int uid_t;
typedef int gid_t;
#endif
So either that's not true anymore, or we're including things in the wrong order, I think.
I'm not sure where those are supposed to come from - they're not mentioned anywhere in plperl. But maybe they're leaking in from the global perl headers?
We could fix this by just changing the parameters to the tarCreateHeader() function to take int instead of uid_t, but that seems like the wrong fix to me. We should at least try to figure out why it's happening in the first place. What happens if you just remove that #ifndef on a win build with perl (sorry, don't have one around at the time - so if you have one, it would me much helpful if you could test it) - do we get a different error, or have we changed around the code and just forgotten that ifdef?
