Fix descrition of pg_resetxlog -l parameter

This was changed in commit 038f3a05092365eca070bdc588554520dfd5ffb9, including
the description in the docs, but the reference was missed.

Fujii Masao
Winflex binary on FTP site doesn't work on 64-bit Windows, update docs.

Plus some other minor clarifications to Windows build instructions.

Craig Ringer, with minor editorialization by me.
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.

Zoltan Boszormenyi and Magnus Hagander
Add new file to MSVC build system as well
Update copyrights for 2013

Fully update git head, and update back branches in ./COPYRIGHT and
legal.sgml files.