Rename various shared library functions

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.

repmgr.control

@@ -1,8 +1,7 @@
 # repmgr extension
 comment = 'Replication manager for PostgreSQL'
-default_version = '5.2'
+default_version = '5.3'
 module_pathname = '$libdir/repmgr'
 relocatable = false
 schema = repmgr
 
-