Document Etags regexp char escape sequences.

etc/NEWS

@@ -593,6 +593,9 @@ be used (only once) in place of a file name on the command line.  Etags
 will read from standard input and mark the produced tags as belonging to
 the file FILE.
 
+*** Regular expressions can use char escape sequences as in Gcc
+These are the escapes \a, \b, \d, \e, \f, \n, \r, \t, \v.
+
 +++
 ** The command line option --no-windows has been changed to
 --no-window-system.  The old one still works, but is deprecated.

etc/etags.1

@@ -168,6 +168,9 @@ such that more characters than needed are unavoidably matched by
 \fItagregexp\fP, it may be useful to add a \fInameregexp\fP, to
 narrow down the tag scope.  \fBctags\fP ignores regexps without a
 \fInameregexp\fP.  The syntax of regexps is the same as in emacs.
+The following character escape sequences are supported:
+\\a, \\b, \\d, \\e, \\f, \\n, \\r, \\t, \\v.
+
 .br
 Here are some examples.  All the regexps are quoted to protect them
 from shell interpretation.

man/maintaining.texi

@@ -485,9 +485,30 @@ where @var{tagregexp} is used to match the lines to tag.  It is always
 anchored, that is, it behaves as if preceded by @samp{^}.  If you want
 to account for indentation, just match any initial number of blanks by
 beginning your regular expression with @samp{[ \t]*}.  In the regular
-expressions, @samp{\} quotes the next character, and @samp{\t} stands
-for the tab character.  Note that @code{etags} does not handle the other
-C escape sequences for special characters.
+expressions, @samp{\} quotes the next character, and all the
+@code{gcc} character escape sequences are supported.  Here is the list
+of the character escape sequences:
+
+@table @samp
+@item \a
+BEL (bell).
+@item \b
+BS (back space).
+@item \d
+DEL (delete).
+@item \e
+ESC (delete).
+@item \f
+FF (form feed).
+@item \n
+NL (new line).
+@item \r
+CR (carriage return).
+@item \t
+TAB (horizontal tab).
+@item \v
+VT (vertical tab).
+@end table
 
   The syntax of regular expressions in @code{etags} is the same as in
 Emacs.  However, non-greedy operators and shy groups are not