3-clause bsd license including advertisement clause

[Klaus Heinz <k.heinz%janzehn.kh-22.de@localhost>]

Hi,

math/p5-Math-BigInteger contains two 3-clause bsd licenses which both
include the advertisement clause but not the fourth clause ("do not promote
without permission").

So far we have original-bsd, 2-clause-bsd and modified-bsd (= 3-clause
without advertisement but with "do not promote without permission").

I think we need a fourth, modified-bsd-with-advertisement.

ciao
     Klaus