add strerror_l(3) to strerror(3)

@@ -50,6 +50,10 @@
 .sp
 .BI "char *strerror_r(int " errnum ", char *" buf ", size_t " buflen );
             /* GNU-specific */
+.sp
+.B #include <locale.h>
+.sp
+.BI "char *strerror_l(int " errnum, " locale_t " loc );
 .fi
 .sp
 .in -4n

@@ -133,6 +137,11 @@
 .I errnum
 is unknown).
 The string always includes a terminating null byte (\(aq\\0\(aq).
+
+To get an error message in a specific locale you need
+.BR strerror_l ()
+it takes an additional argument that defines to locale in what the message is returned.
+The function is thread-safe.
 .SH RETURN VALUE
 The
 .BR strerror ()

@@ -180,6 +189,8 @@
 .LP
 The
 .BR strerror_r ()
+and
+.BR strerror_l ()
 function is thread-safe.
 .SH CONFORMING TO
 .BR strerror ()

@@ -210,6 +221,41 @@
 .B EINVAL
 if the error number is unknown.
 C99 and POSIX.1-2008 require the return value to be non-NULL.
+.sp
+.BR strerror_l ()
+is a POSIX.1-2008 requirement, but available as GNU-specific function
+at least since glibc 2.6.1.
+.SH EXAMPLE
+The program below demonstrates the use of the
+.BR strerror* ()
+functions. The first line of output should be
+.I strerror_l(13)=Permission denied
+the others should print this in a locale as specified by
+.B LANG
+variable.
+.nf
+
+#include <stdio.h>
+#include <string.h>
+#include <locale.h>
+
+int main()
+{
+  int e=13;    // errornumber
+  char buf[255];
+  locale_t loc;
+
+  setlocale(LC_ALL, "");
+  loc = newlocale (LC_MESSAGES_MASK, "C", NULL);
+  printf("strerror_l(13)=%s\\n",strerror_l(e,loc));
+  freelocale (loc);
+  // this will be translated automaticly
+  printf("strerror(13)=%s\\n",strerror(e));
+  strerror_r(e,buf,sizeof(buf)-1);
+  printf("strerror_r(13)=%s\\n",buf);
+  return 0;
+}
+.fi
 .SH SEE ALSO
 .BR err (3),
 .BR errno (3),