Missing illuminant array elements

[nbvdkamp]

While porting this repo to another language, I noticed that the cie_d50 and cie_d60 arrays in details/cie1931.h have only 94 out of 95 elements assigned, meaning the remaining element is zero initialized. For d50 this does not make a difference (I think) since it ends in zeros but for d60 it may actually matter.

It's probably not a large enough discrepancy that anyone would ever notice but I thought I should let you know.