Use Xr to reference timespec(2)

gistfile1.txt

Index: kqueue.2
===================================================================
RCS file: /cvsroot/src/lib/libc/sys/kqueue.2,v
retrieving revision 1.39
diff -u -r1.39 kqueue.2
--- kqueue.2    11 Apr 2017 11:06:39 -0000      1.39
+++ kqueue.2    11 Apr 2017 11:20:31 -0000
@@ -133,7 +133,8 @@
 is a
 .No non- Ns Dv NULL
 pointer, it specifies a maximum interval to wait
-for an event, which will be interpreted as a struct timespec.
+for an event, which will be interpreted as a struct
+.Xr timespec 2 .
 If
 .Fa timeout
 is a
@@ -146,7 +147,7 @@
 argument should be
 .No non- Ns Dv NULL ,
 pointing to a zero-valued
-.Va timespec
+.Xr timespec 2
 structure.
 The same array may be used for the
 .Fa changelist
@@ -641,6 +642,7 @@
 .Xr read 2 ,
 .Xr select 2 ,
 .Xr sigaction 2 ,
+.Xr timespec 2 ,
 .Xr unlink 2 ,
 .Xr write 2 ,
 .Xr signal 3 ,