BUG #8500: Upgrade to postgis 2.1 breaks existing databases

The following bug has been logged on the website:

Bug reference: 8500
Logged by: Kriton Kyrimis
Email address: kyrimis(at)alumni(dot)princeton(dot)edu
PostgreSQL version: 9.2.4
Operating system: Scientific Linux 6.4
Description:

The version of postgis, available in the postgresql yum repository for
postgis 9.2, was recently upgraded to version 2.1. This breaks existing
databases built with postgis 2.0, as queries involving postgis fail with the
error message "ERROR: could not access file "$libdir/postgis-2.0": No such
file or directory"

This includes backing up the databases, so upgrading them to use postgis 2.1
may not even be an option, if a hard upgrade is required.

I have downgraded all postgis2_92 packages to version 2.0.4 and excluded
them from future upgrades, but I'd recommend reverting to that version in
the repositories, as well. At the very least, please ensure that version
2.0.x of the packages remains available in the future. Better still, provide
alternative postgis21_92-* packages, for those wishing to use the latest
version, without affecting those that use the previous version.