Provide more structure/derived data type analysis

[raehik]

Based on a conversation with @RaoulHC , we don't appear to gather type information for structures/derived data types during type analysis. The analysis at Analysis.Types outputs a TypeEnv = Map Name IDType. We could build and output a Map Name (Map Name IDType) alongside it that maps DDT/record type names to a map of their fields & corresponding types.

[dorchard]

Is this also a problem in fotran-vars?

[RaoulHC]

The StructureTable module in fortran-vars deals with this, so if we're to move over to using information from the analysis phase we'll need it to do something similar to that.

[raehik]

Support for regular fields (not union, internal structure extensions) added in #175 thanks to @RaoulHC . I'll keep this issue around for a while -- interested in seeing if there's any way we can improve transformations or analyses in CamFort with this new info.