(Closes #2538) Added a preprocessor interface

[LonelyCat124]

[LonelyCat124]

@sergisiso this is done (I think?), it doesn't really add a lot by itself but it should be useful for the Otter stuff.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.85%. Comparing base (496ad4c) to head (f64500f). Report is 2 commits behind head on master.

:exclamation: Current head f64500f differs from pull request most recent head 48ff0a2. Consider uploading reports for the commit 48ff0a2 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2539   +/-   ##
=======================================
  Coverage   99.85%   99.85%           
=======================================
  Files         356      356           
  Lines       47831    47834    +3     
=======================================
+ Hits        47762    47765    +3     
  Misses         69       69           

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[LonelyCat124]

@sergisiso Should have added the changes you requested here now.

[LonelyCat124]

Hmm, the test isn't currently working so I'll check this tomorrow.

[LonelyCat124]

@sergisiso Ok, I had to add something to the backend to ignore PreprocessorInterface symbols but this should be ready for another look now.