string.3, strlen.3, strnlen.3: Use 'bytes' not 'characters'

This is inline with POSIX terminology. See also the earlier
commit a00b7454b8 (in 2012)
which fixed most of these cases.

Reported-by: Jakub Wilk <jwilk@jwilk.net>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man3/string.3

@@ -46,7 +46,7 @@ ignoring case.
 .BI "int strncasecmp(const char *" s1 ", const char *" s2 ", size_t " n );
 Compare the first
 .I n
-characters of the strings
+bytes of the strings
 .I s1
 and
 .I s2
@@ -132,7 +132,7 @@ Return the length of the string
 .BI "char *strncat(char *" dest ", const char *" src ", size_t " n );
 Append at most
 .I n
-characters from the string
+bytes from the string
 .I src
 to the string
 .IR dest ,
@@ -199,7 +199,7 @@ Transforms
 .I src
 to the current locale and copies the first
 .I n
-characters to
+bytes to
 .IR dest .
 .SH DESCRIPTION
 The string functions perform operations on null-terminated

man3/strlen.3

@@ -45,7 +45,7 @@ excluding the terminating null byte (\(aq\\0\(aq).
 .SH RETURN VALUE
 The
 .BR strlen ()
-function returns the number of characters in the string pointed to by
+function returns the number of bytes in the string pointed to by
 .IR s .
 .SH ATTRIBUTES
 For an explanation of the terms used in this section, see

man3/strnlen.3

@@ -41,7 +41,7 @@ _GNU_SOURCE
 .SH DESCRIPTION
 The
 .BR strnlen ()
-function returns the number of characters in the string
+function returns the number of bytes in the string
 pointed to by
 .IR s ,
 excluding the terminating null byte (\(aq\\0\(aq),