Add class(*) back to mixedmode diag_manager

[mlee03]

Description
All class(*) related code in FMS has been removed including diag_manager for the mixed-mode work. This leads to model compilation errors. Thus in this PR, class(*) related code has been added back todiag_manager in the mixedmode branch.

Fixes # (issue)

How Has This Been Tested?
FMS compiles with Intel

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included
• make distcheck passes

[thomas-robinson]

Does this merge with the dmUpdate branch?

[mlee03]

@thomas-robinson Marvelous news, it does! We'll make sure to keep it that way too.

[thomas-robinson]

@thomas-robinson Marvelous news, it does! We'll make sure to keep it that way too.

...and the tests pass? Can you create a new PR in dmUpdate so we can look at the differences on here?