Choosing Between Pacemaker 1.1 and 2.0

Distribution packagers, and users who build Pacemaker themselves, will need to choose between staying on the 1.1 line or moving to 2.0. Factors to consider:


 * 1.1 supports the Heartbeat and Corosync 1 stacks, 2.0 does not
 * 1.1 (starting with 1.1.18) logs warnings if any of the legacy syntax removed in 2.0 is used (this is of particular interest to distributions that want those warnings in at least one release)
 * 2.0 breaks rolling upgrades from Pacemaker 1.1.10 and earlier on corosync 2 (and of course from any version on other stacks)
 * Only 2.0 will be actively developed from this point, but at least some bug fixes will be backported to the 1.1 branch for the foreseeable future, and we will eventually do at least one more 1.1 release with those fixes
 * The 2.0 code base will be different enough that it will be difficult to backport changes there to 1.1 (in case anyone was considering doing so)
 * The feature removals in 2.0 were done in distinct commits as much as possible, so it should be feasible (if nontrivial) to revert commits to re-enable particular features, if backward compatibility for those are desired
 * See Pacemaker 2.0 Changes for a detailed list of what changed