ghidra: some 16-bit enums should have 32-bit versions

There's any number of enums (e.g. `job_type`) that we have defined as 16-bit but which are often handled internally as 32-bit. Having them defined only as 16-bit enums makes marking up decompiled code harder.

`import_df_structures` should therefore probably create a 32-bit version for any enum that is officially sized as 16-bit.