Functions splice and vmsplice in glibc 2.5 not being declared for c progam

Feisty Fawn appears to almost support splice and vmsplice - the functions are in declared /usr/include/bits/fnctl.h, and are defined in the glibc library , but for some reason the declarations do not seem to be available during my compile:
(splice and vmsplice are new functions added in linux kernel 2.6.17, and supported by glibc 2.5)

 echo '#include <fcntl.h>
int main(){ vmsplice(0,0,0,0,0,0); return 0;}' > dummy.c && gcc -Wall dummy.c

result in:
dummy.c: In function ‘main’:
dummy.c:2: warning: implicit declaration of function ‘vmsplice’

The result with splice is the same.