[VM] Bug or feature that vm-imap-folder-p not defined when vm loaded?

[kosowskyj]

The function vm-imap-folder-p is in vm-save which doesn't seem to be autoloaded 
when vm
is started. This causes an error for me since I use vm-imap-folder-p
in the vm-mode-hook. I can of course avoid this error by running
(require 'vm-save) first but should this be necessary?

I.e. isn't vm-imap-folder-p an important enough predicate that it should just be
there initially and shouldn't require manual loading of vm-save