pgsql: In pg_upgrade, pull the port number from postmaster.pid, like we

In pg_upgrade, pull the port number from postmaster.pid, like we do for
socket location.  Also, prevent putting the socket in the current
directory for pre-9.1 servers in live check and non-live check mode,
because pre-9.1 pg_ctl -w can't handle it.

Backpatch to 9.2.

Branch
------
REL9_2_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/d0a51117da92efd8cba426f6591fc1cfe6a497a3

Modified Files
--------------
contrib/pg_upgrade/check.c      |   16 +++++---
contrib/pg_upgrade/option.c     |   84 +++++++++++++++++++++++----------------
contrib/pg_upgrade/pg_upgrade.c |    3 +-
3 files changed, 62 insertions(+), 41 deletions(-)