Add a system to deal with reduced header MAT files.

Files produced by Simulink, along with embedded MAT files inside of MAT files
don't have the full header.  Thus enable parsing them as necessary.
Add in the beginnings of an MCOS parser.

MCOS is handled completely separately through a weird format.  Thus, start
supporting it by reading in the necessary data.  Currently it isn't fully
parsed, as the first unit test doesn't require extra data.  Also include the
MATLAB class file used to generate the test.
Minor code style.

Fix some comment misspellings and formatting, and remove unused imports.