- Remove xbps_repo_get_plist() and try to internalize all members at
xbps_repo_open() time.
- Added xbps_repo_open_idxfiles() to also internalize the index-files
plist from repository, which is really huge and must only be internalized
when needed.
- Improve how signed and verified repositories are detected.
- Misc optimizations and small performance improvements.
Bump XBPS_API_VERSION.