Concatenating Structure Arrays with Different Fields

When I read data from the web, using webread or websave, usually all records returned have the same information and, as a result, appear in MATLAB as a struct array. But sometimes they do not have the same information and appear as a cell array containing structures with different fields. This has recently happened in one of my scripts, so I need to address this and I think it would be useful for me come up with a utility to handle this scenario in general as it often happens.

(Originally posted on Stuart's MATLAB Videos blog.)