Fix incremental archiving of renamed directories.

Fix incremental archiving of renamed directories.

* src/incremen.c (struct directory): New member `next'.  Change
type of `name'.
(dirhead, dirtail): New statics.
(make_directory): Reflect changes to struct directory.
(free_directory, attach_directory): New functions.
(dirlist_replace_prefix): New function.
(note_directory): Use attach_directory, instead of make_directory,
(find_directory, find_directory_meta): Use free_directory.
(procdir): Replace directory prefixes in directory list to avoid
marking subdirectories as renamed after renaming their parent
directory.
(append_incremental_renames): Iterate over directory list, not
hash table, to preserve logical ordering of renames.
* tests/rename04.at, tests/rename05.at: New test cases.
* tests/Makefile.am, tests/testsuite.at: Add rename04.at and
rename05.at.
* tests/atlocal.in (decho): New function.
* tests/multiv06.at: Use decho instead of echo2.
* tests/incremental.at: Raise wait interval to 2 seconds.