wrong result when using auxillary coordinate with _Fillvalue

[bertulus]

The cfchecker gives a Information (_Fillvalue used in a non standard way) when a auxiliary coordinate has a _FillValue attribute. The current CF-conventions explicitly allow this.

[RosalynHatcher]

Thank you for reporting this. I will update the checker at the earliest opportunity.

Note to self: This change applies from CF-1.6 onwards.