fix: filter precedence, files-from errors, NUL/CRLF and filter-rule rejections

Address an independent c-review of the files-from/filter feature:

- .rsync-filter precedence now matches rsync: evaluate the innermost
  (current) directory's rules first, then ancestors, then the command-line
  base (--filter/-C), so a deeper file's '+' can re-include what a shallower
  '-' excluded (regression tests in both scan modes; single-thread and -m).
- --files-from: a listed entry missing on disk and an empty list are now hard
  errors surfaced pre-transfer in send_files, send_files_multithreaded,
  dry-run and --list-only; '.' (whole tree) and empty listed dirs stay valid.
- scanner_path_relative now handles a transfer root of / (previously the
  scanner aborted on children of /).
- Reject unsupported rsync filter syntax explicitly (no silent no-ops):
  +/- modifiers other than '/' (! C s r p x) and rules beginning with ':'/'.'
  /'!' (merge/dir-merge/list-clear shorthands). Docs updated.
- -0/--from0 NUL mode preserves entry bytes (no CR/LF trimming); only newline
  mode trims. Absolute-entry error message no longer includes the newline.
- --no-from0/--no-cvs-exclude registered as negatable booleans.
- RSYNC_COMPAT rows updated for the precedence, rejection list, NUL-mode
  detail and the documented O(entries x files) scalability bound of the
  allow-set (Summary unchanged: 62/3/5/1/76 = 147).

src/client/client_cli.c

@@ -473,6 +473,8 @@ static const NegatableOption NEGATABLE_OPTIONS[] = {
     {"sparse", "S", offsetof(Config, preserve_sparse)},
     {"inplace", NULL, offsetof(Config, inplace)},
     {"checksum", NULL, offsetof(Config, checksum)},
+    {"from0", NULL, offsetof(Config, from0)},
+    {"cvs-exclude", NULL, offsetof(Config, cvs_exclude)},
 
     /* These options are also implied by --archive or handled outside the table. */
     {"compress", "c", offsetof(Config, use_compression)},