MINOR: ssl: Add a cafile_entry type field

MINOR: ssl: Add a cafile_entry type field

The CA files and CRL files are stored in the same cafile_tree so this
patch adds a new field the the cafile_entry structure that specifies the
type of the entry. Since a ca-file can also have some CRL sections, the
type will be based on the option used to load the file and not on its
content (ca-file vs crl-file options).