COMP: explicitly handle all enum cases in switch

COMP: explicitly handle all enum cases in switch

In VisualStudio 2019 error C4061 happens if you don't
have a case statement for every value of an enum.
The default condition is not enough.

This fix avoids error like this:

25>C:\sq5\LibArchive\libarchive\archive_read_support_format_warc.c(344,2): error C4061: enumerator 'WT_NONE' in switch of enum 'warc_type_t' is not explicitly handled by a case label [C:\sq5\LibArchive-build\libarchive\archive.vcxproj]