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

After research, We think malloc_stats() is thread-safe. But, there
is not marking of malloc_stats() in glibc document.
- malloc_stats: MT-Safe

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

man3/malloc_stats.3

@@ -52,6 +52,19 @@ allocated using
 .BR mmap (2).
 .\" .SH VERSIONS
 .\" Available already in glibc 2.0, possibly earlier
+.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 malloc_stats ()
+T}	Thread safety	MT-Safe
+.TE
+
 .SH CONFORMING TO
 This function is a GNU extension.
 .SH NOTES