R-devel on FreeBSD: new C99 functions don't build

About April 25th, there had been some changes within R-devel's
src/nmath/pnbeta.c (and probably some other relevant places) and now
building R-devel on FreeBSD 10.0-CURRENT (amd64) with gcc-4.6.4 and
math/R-devel (selfmade forked port from math/R) fails like this:

It seems, that at least one new C99 function (log1pl) is introduced in
R-devel, see

src/nmath/pnbeta.c:l95
return (double) (log_p ? log1pl(-ans) : (1 - ans));

AFAIK, Bruce Evans is not happy with the numerical accuracy of other
open-source implementations of log1pl and so has blocked their
inclusion in FreeBSD pending work on a better implementation.

Can you put a conditional FreeBSD check here and use log1p instead of
log1pl instead as a workaround?

I can admire the insistence on correctness from the FreeBSD libm
maintainers for their technical purity, but it can be a bit of a pain
for things like this.

         - Murray