CPAN/Meta: add mozilla_2_0

[rehsack]

Add mozilla_2_0 to allow better solution for gisle/mozilla-ca#11 (https://rt.cpan.org/Ticket/Display.html?id=97815)

According to https://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/meta/files/common-licenses there're a lot of licenses missing. A reasonable number (as n-clause BSD licenses, CC-BY-, AFL-, ...) could be easily added.

Just drop me a note and I do at least the low-hangin-fruits.

[Leont]

The spec only allows a small list of values as license strings. As such, accepting this would violate the spec.

IMO, the long term solution would be to add a new SPDX-license extension field.

[karenetheridge]

Agreed, any modifications to the spec itself would require a version bump (which is not out of the question -- but we need to be aware we are doing it).