pgsql: Run pg_upgrade and pg_resetxlog with restricted token on Windows

Run pg_upgrade and pg_resetxlog with restricted token on Windows

As with initdb these programs need to run with a restricted token, and
if they don't pg_upgrade will fail when run as a user with Adminstrator
privileges.

Backpatch to all live branches. On the development branch the code is
reorganized so that the restricted token code is now in a single
location. On the stable bramches a less invasive change is made by
simply copying the relevant code to pg_upgrade.c and pg_resetxlog.c.

Patches and bug report from Muhammad Asif Naeem, reviewed by Michael
Paquier, slightly edited by me.

Branch
------
REL9_4_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/2366761bf9eb8e9aa3820b9f3491bcfc48b8188f

Modified Files
--------------
contrib/pg_upgrade/pg_upgrade.c | 166 +++++++++++++++++++++++++++++++++++
src/bin/pg_resetxlog/pg_resetxlog.c | 166 +++++++++++++++++++++++++++++++++++
2 files changed, 332 insertions(+)