Primary Mensuration Issue

[benory]

When there are multiple mensuration signs in a given piece, it is good to use !!primary-mensuration: met() to indicate the mensuration from which the tempo should be derived. But a bug in primary-mensuration is overriding the visible mensuration signs.

For example, in Mlu2002, when primary-mensuration is added to the humdrum file, it now appears (both in VHV and rendered on the website) that all five voices are in Cut-C mensuration, when in fact the tenor II voice is in C mensuration.

[benory]

@craigsapp Can you take a look at this?