Import libcerf-1.4 as devel/libcerf.

This is libcerf, a self-contained numeric library that provides an
efficient and accurate implementation of complex error functions,
along with Dawson, Faddeeva, and Voigt functions.

On current GNU/Linux systems, the man page complex(7) has a "see
also" section that lists complex mathematical functions like cabs(3),
cacos(3), and so on. Among them, there is a complex error function.
However, its manual page cerf(3) describes the functions cerf and
cerfc as "unimplemented" and "reserved for future use". The present
library libcerf provides the missing implementation, along with a
related functions. It comes with a set of man pages, including a
page cerf(3) that overwrites the standard one.

(wiz)