bsearch.3: ATTRIBUTES: Note function that is thread-safe

The marking matches glibc marking.
The marking of functions in glibc is:
- bsearch: MT-Safe

Signed-off-by: Zeng Linggang <zenglg.jy@cn.fujitsu.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man3/bsearch.3

@@ -74,6 +74,19 @@ function returns a pointer to a matching member of the
 array, or NULL if no match is found.
 If there are multiple elements that
 match the key, the element returned is unspecified.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lb lb lb
+l l l.
+Interface	Attribute	Value
+T{
+.BR bsearch ()
+T}	Thread safety	MT-Safe
+.TE
+
 .SH CONFORMING TO
 SVr4, 4.3BSD, POSIX.1-2001, C89, C99.
 .SH EXAMPLE