Sieve can't find Extprograms or Extdata

[E.B.]

Also, of course I have entered this in 90-plugins.conf

plugin {
  seive_plugins = sieve_extdata sieve_extprograms
  sieve_extensions = +vnd.dovecot.filter +vnd.dovecot.extdata
}

And enabled sieve for lmtp (as I noted, I have tested that simple
sieve scripting is working OK)

protocol lmtp {
  mail_plugins = " sieve"
}


> On a new install-from-source with Dovecot 2.2.16rc1,
> Piegeonhole 0.4.6 and a grab of the newest Extdata code, I
> confirmed basic Sieve functionality is working (made a
> simple sieve script with a test on message subject resulting
> in a fileinto action).
> 
> But I cannot get Sieve to see Extdata or Extprograms. sievec
> reports "Warning: sieve: ignored unknown extension
> 'vnd.dovecot.filter' while configuring available extensions"
> and the same for vnd.dovecot.extdata.  And of course
> for the user script, "error: require command: unknown Sieve
> capability `vnd.dovecot.filter'" (same with extdata)
> 
> I'm pretty sure this is a library path problem, but I've
> tried symlinking and restarting dovecot with as many
> iterations of library paths as I can think of but still same
> problem.
> 
> The lib90_sieve_extdata_plugin.so and
> lib90_sieve_extprograms_plugin.so are in
> /usr/local/lib/dovecot/sieve and all the rest of the normal
> dovecot libraries are one level above in
> /usr/local/lib/dovecot.
> 
> I tried creating symlinks for a "modules" directory and a
> "modules/sieve" directory, I tried symlinking these two
> librarie files themselves into the top level dovecot library
> directory, and a few other ideas, but no luck.
> 
> Is there a way I can tell where Sieve expects its libraries
> to reside? To see where it is looking? I didn't provide any
> arguments to the configure command for pigeonhole as well as
> extdata and it seems like the libs got placed somewhere
> sensible, but I don't know what else to do.