Clarify utimes() behaviour when 'times' is NULL. See Debian bug 431480.

Other minor clarifations of description of utimes().

man2/utime.2

@@ -82,15 +82,12 @@ struct utimbuf {
 The function
 .BR utime ()
 allows specification of time stamps with a resolution of 1 second.
+.SS utimes()
 The function
 .BR utimes ()
-is similar, but allows a resolution of 1 microsecond.
-Here
-.IR times [0]
-refers to access time, and
-.IR times [1]
-to modification time.
-
+is similar, but the
+.I times
+argument allows a resolution of 1 microsecond for the timestamps.
 The
 .I timeval
 structure is:
@@ -103,6 +100,17 @@ struct timeval {
 };
 .fi
 .RE
+.PP
+.IR times [0]
+specifies the new access time, and
+.IR times [1]
+specifies the new modification time.
+If
+.I times
+is NULL, then analogously to
+.BR utime (),
+the access and modification times of the file are
+set to the current time.
 .SH "RETURN VALUE"
 On success, zero is returned.
 On error, \-1 is returned, and