Check if variables set by DATA statements could be made named constants (parameters)

[Beliavsky]

Many old codes set variables that never changed and could be named constants using the DATA statement. I suggest that Fortitude warn about such code and eventually have the ability to fix it by declaring the variables as parameter. An example of code that could be rewritten this way is at https://github.com/UoA-Stars-And-Supernovae/STARS/blob/master/src/diffusion2.f -- variables BARYN AND MIZZ could have the parameter attribute.

[ZedThree]

I guess we can do this in the case where the variable isn't used in a common block, doesn't appear on the left hand side of an assignment, and also isn't passed to any subroutine or function calls -- in the future, if we have more semantic information, we might be able to check the intents, and follow uses through common blocks.

At that point, we might also be able to do similar analysis for all variables (although potentially this is an expensive check!)