Some of the more generically named functions are at risk of colliding
with functions defined in other libraries. To mitigate that risk,
prefix with "repmgr_", unless the name already has some reference
to repmgr.
This requires an extension version bump.
RM20471.
Note that the next release is intended to be 5.0 to coincide with the
release of PostgreSQL 12; 4.5 is currently a placeholder in case we
need to push out a feature release before then.
