wc: fix missing documentation for the --debug option

* doc/coreutils.texi (wc invocation): Desscribe --debug.
* src/wc.c (usage): Likewise.
* NEWS: Mention the bug fix.

NEWS

@@ -8,6 +8,10 @@ GNU coreutils NEWS                                    -*- outline -*-
   This also applies to the sha*sum and b2sum utilities.
   [This bug was present in "the beginning".]
 
+  wc now documents its --debug option, currently used to
+  indicate the line count acceleration being used.
+  [bug introduced in coreutils-9.0]
+
 
 * Noteworthy changes in release 9.9 (2025-11-10) [stable]
 

doc/coreutils.texi

@@ -3992,6 +3992,11 @@ Print only the newline character counts.
 If a file ends in a non-newline character,
 its trailing partial line is not counted.
 
+@item --debug
+@opindex --debug
+Output extra information to standard error.
+Currently; print the line count acceleration implementation being used.
+
 @item -L
 @itemx --max-line-length
 @opindex -L

src/wc.c

@@ -187,6 +187,9 @@ the following order: newline, word, character, byte, maximum line length.\n\
   -c, --bytes            print the byte counts\n\
   -m, --chars            print the character counts\n\
   -l, --lines            print the newline counts\n\
+"), stdout);
+      fputs (_("\
+      --debug            indicate what line count acceleration is used\n\
 "), stdout);
       fputs (_("\
       --files0-from=F    read input from the files specified by\n\