Updates for 7.2 INSTALL file

Hi all,

With the INSTALL file, do we change the references from 7.1 to 7.2 now
or wait until later? (Not counting the "Supported Platforms" bit)

Found three instances where 7.1 should be 7.2, not sure about the one
which mentions that pg_dumpall of 7.1 shouldn't be used on older
versions of the database.

Have generated a diff in case that's the easiest way for the change to
be applied.

Regards and best wishes,

Justin Clift

--
"My grandfather once told me that there are two kinds of people: those
who work and those who take the credit. He told me to try to be in the
first group; there was less competition there."
- Indira Gandhi