iconv and configure

HI,

I needed to use an alt-charset today for an smsc connection but found  
when I added the option that no conversion was being done on inbound  
sms :-

2007-03-26 08:32:21 [44173] [6] ERROR: Failed to convert msgdata from  
charset <ISO-8859-15> to <UTF-8>, will leave as is.

On investigation I see that, under FreeBSD (6.2), configure is not  
picking up the existence of either  iconv.h or libiconv. The are both  
installed :-

$ ls /usr/local/include/iconv.*
/usr/local/include/iconv.h

$ ls /usr/local/lib/libiconv.*
/usr/local/lib/libiconv.a       /usr/local/lib/libiconv.la      /usr/ 
local/lib/libiconv.so      /usr/local/lib/libiconv.so.3

I have to admin that the whole configure thing is a black art mystery  
to me, so how please can somebody who practices in these arts, tell  
me how do I update configure so that it will find and use this library.

Regards

Ben