Access to localized_str_tolower()

Howdy,

In my original implementation of citext, which I'm going to start  
using for an app I'm developing, I pull in the wstring_lower function  
from oracle_compat.c by simply declaring it at the top of citext.c,  
just as if it were in an include file:
  extern char * wstring_lower  (char *str);

After I ported it to CVS HEAD, however, and discovered the  
str_tolower() function in formatting.c, I wanted to try to make use of  
it in 8.3, as well. But when I tried to include it in citext.c, it  
simply didn't work. I put this at the top of citext.c:
  extern char * localized_str_tolower(char *buff);

But when I try to use it, like so:
    lcstr = localized_str_tolower(VARDATA_ANY(left));    rcstr = localized_str_tolower(VARDATA_ANY(right));

I get a compile-time error:

Undefined symbols:  "_localized_str_tolower", referenced from:      _citextcmp in citext.o      _citextcmp in citext.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
make: *** [citext.so] Error 1

So, stupid C question, I'm sure: How can I use this function from my  
module?

Oh, and on a side note, should I localized_str_tolower() or just  
str_tolower()?

Thanks,

David