daemon_filter_list, for improved clarity.

- Die if the --server option is not first on the command-line.
- Don't allow the --daemon option by default.

The generator can skip a directory's contents altogether due to
--ignore-non-existing, a daemon exclude, or a mkdir failure.  On a
--dry-run, the generator can also note the missingness of a directory
while still scanning its contents.  These two scenarios were conflated
using a single set of missing_below/missing_dir variables in combination
with transient increments in dry_run; this caused at least three bugs.

Now recv_generator has separate variables for the two scenarios, called
skip_dir and dry_missing_dir, respectively.  For simplicity, we take the
F_DEPTH instead of having separate *_below variables.  We mark both
kinds of missing dirs with FLAG_MISSING_DIR.  (dry_run > 1) iff the
*root* of the destination does not exist; it is no longer incremented
for missing subdirs.  I added tests for the three fixed bugs in
missing.test.

the various filter parameters.

avoid a daemon-exclude.

work better.

silently ignoring them.

try to turn off unused-parameter compiler warnings.

the FLAG_SKIP_HLINK flag, which gets set on any hard-linked file that
the user wants to skip (e.g. via --ignore-existing, --append, etc.).
The code in hlink.c now deals with the skipped files instead of
triggering an assert() error.

still get their non-content attributes updated, and combining --append
with --hard-links will not prevent the discovery of unchanged files.

a dir/symlink/device/special-file, just like it already refuses to
overwrite a non-regular file with a regular file.

while requesting a file-listing and we suspect that the remote rsync
is complaining about the -d option.

  create a directory in the backup-path area.
- Fixed a bug where make_file() was setting F_PATHNAME() on the
  receiving side.
- A non-pool (temp-memory) file structure now stores the size of
  its extra_cnt value in the F_DEPTH() int so that unmake_file()
  can always be sure of how to free() the memory.
- The ACL-preserving code no longer allocates 4 more bytes per
  file entry than it needs.
- Got rid of a useless adding of the symlink length to "bp".

(rather than /usr/include/popt.h), and use the included popt lib
if it is (to avoid a potential conflict due to our use of -I.).

when talking to older rsync versions.

  the client on the receiving side of a protocol-29 connection.

- If a symlink/device/special-file changes its value without any
  attribute changes, the itemized event no longer gets dropped.
- We put a 'c' into the checksum/change field now to indicate when
  a symlink/device/special-file changes its value without changing
  its type.  This lets us properly interpret the --copy-links output
  to know which items are getting copied without changes and which
  are getting created with new content.
- Fixed the 'T' itemized output for a symlink when rsync tries to
  set the right time but fails due to lack of OS/disk support.