[CF-metadata] regions

[Jonathan Gregory]

Dear Brian

> Frank Bryan at NCAR was requesting "Indo-Pacific" for a region, which I 
> guess is commonly used for calculating northward ocean heat transport in 
> those basins.

This sounds reasonable to me. Brian, would you be happy to add
indo_pacific_ocean to the list of regions? I would say that the inclusion
of global_ocean and eurasia in the list are precedents for combined regions.

Best wishes

Jonathan