comms/asterisk18 lacks spandsp support

[Stefano Marinelli <postnet%dragas.dyndns.org@localhost>]

Hello,
I've successfully built Asterisk 1.8 from pkgsrc because I am planning to 
switch a PBX from Debian Linux to NetBSD (5.1 stable).
Asterisk works, but it has just faxing support over T38 and not the 
(unreliable, but often useful) Audio fax transmission. This is acheived using 
the "spandsp" library (not present in pkgsrc, just in wip). But actually the 
Asterisk in pkgsrc doesn't support it at all. I've tried to compile the wip one 
and install it, modify the Makefile to enable the support but the build stops 
because it cannot find the spandsp files (correctly present in 
/usr/pkg/include).
Did anybody ever had this problem/solved in any way? Thank you!