Log Message:
tex-metapost-colorbrewer{,-doc}: add version 2018

This package provides two MetaPost include files that define
all the colorbrewer2.org colours: colorbrewer-cmyk.mp
colorbrewer-rgb.mp The first defines all the colours as CMYK,
the second as RGB. Use whichever one you prefer. For an example
of what you can do, and a list of all the names, have a look at
colorbrewer-sampler.mp. You can also see the names on
http://colorbrewer2.org.