On OpenBSD, both sys/mount.h and sys/sysctl.h require sys/param.h in order

to compile.  With recent Autoconf versions, AC_CHECK_HEADERS only succeeds
if the header compiles, so need to check these two with sys/param.h
explicitly included in the search list...

This commit was SVN r27715.

configure.ac

@@ -599,15 +599,29 @@ AC_CHECK_HEADERS([alloca.h aio.h arpa/inet.h dirent.h \
     libutil.h memory.h netdb.h netinet/in.h netinet/tcp.h \
     poll.h pthread.h pty.h pwd.h sched.h stdint.h stddef.h \
     stdlib.h string.h strings.h stropts.h sys/fcntl.h sys/ipc.h sys/shm.h \
-    sys/ioctl.h sys/mman.h sys/mount.h sys/param.h sys/queue.h \
+    sys/ioctl.h sys/mman.h sys/param.h sys/queue.h \
     sys/resource.h sys/select.h sys/socket.h sys/sockio.h \
     stdarg.h sys/stat.h sys/statfs.h sys/statvfs.h sys/time.h sys/tree.h \
     sys/types.h sys/uio.h net/uio.h sys/utsname.h sys/vfs.h sys/wait.h syslog.h \
     time.h termios.h ulimit.h unistd.h util.h utmp.h malloc.h \
-    ifaddrs.h sys/sysctl.h crt_externs.h regex.h signal.h \
+    ifaddrs.h crt_externs.h regex.h signal.h \
     ioLib.h sockLib.h hostLib.h shlwapi.h sys/synch.h limits.h db.h ndbm.h \
     TargetConditionals.h])
 
+AC_CHECK_HEADERS([sys/mount.h], [], [],
+[AC_INCLUDES_DEFAULT
+#if HAVE_SYS_PARAM_H
+#include <sys/param.h>
+#endif
+])
+
+AC_CHECK_HEADERS([sys/sysctl.h], [], [],
+[AC_INCLUDES_DEFAULT
+#if HAVE_SYS_PARAM_H
+#include <sys/param.h>
+#endif
+])
+
 # Needed to work around Darwin requiring sys/socket.h for
 # net/if.h
 AC_CHECK_HEADERS([net/if.h], [], [],