check/include sys/select.h if present.

CHANGES

@@ -1,3 +1,6 @@
+untagged yet (2017-06-12)
+    - OpenBSD (and possibly others) need <sys/select.h>
+
 0.1.35-rc (2017-30-05)
 	- Nokia SR OS (formerly Alcatel-Lucent) support. Based on submission by
     Michail Litvak.

bgpq_expander.c

@@ -4,6 +4,9 @@
 
 #include <sys/types.h>
 #include <sys/socket.h>
+#if HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
 
 #include <assert.h>
 #include <fcntl.h>

configure

@@ -3398,7 +3398,7 @@ fi
 done
 
 
-for ac_header in sys/cdefs.h sys/queue.h sys/tree.h
+for ac_header in sys/cdefs.h sys/queue.h sys/tree.h sys/select.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"

configure.in

@@ -3,7 +3,7 @@ AC_CONFIG_HEADER(config.h)
 AC_PROG_CC
 AC_PROG_INSTALL
 
-AC_CHECK_HEADERS([sys/cdefs.h sys/queue.h sys/tree.h])
+AC_CHECK_HEADERS([sys/cdefs.h sys/queue.h sys/tree.h sys/select.h])
 
 AC_MSG_CHECKING([for STAILQ_ interface in queue.h])
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([