- Add fdupes build dependency
- break overlong lines in changelog

* fixed potential index corruption / data loss issue due to bug in
hashindex_set, #4829 Please read and follow the more detailled notes
close to the top of this document.
* upgrade bundled xxhash to 0.7.3, #4891 0.7.2 is the minimum requirement
for correct operations on ARMv6 in non-fixup mode, where unaligned memory
accesses cause bus errors. 0.7.3 adds some speedups and libxxhash 0.7.3
even has a pkg-config file now.
* support platforms without os.link (e.g. Android with Termux), #4901 if
we don't have os.link, we just extract another copy instead of making a
hardlink.
* support linux platforms without sync_file_range (e.g. Android 7 with
Termux), #4905
* argparser: always use REPOSITORY in metavar, also use more consistent
help phrasing.