[collectd] nanosleep configure tests

[Vincent McIntyre]

I found another discussion of this
  http://lists.apple.com/archives/Darwin-development/2002/Apr/msg00408.html
that suggests the patch is more like

- AC_CHECK_FUNCS(nanosleep, [], AC_CHECK_LIB(rt, nanosleep,
nanosleep_needs rt="yes"], AC_MSG_ERROR(cannot find nanosleep)))

+ AC_CHECK_FUNCS(nanosleep,,[AC_CHECK_LIB(rt,nanosleep,LTHREAD_LIBS="$LTHREAD_LIBS
-lrt",[AC_CHECK_LIB(posix4,nanosleep,LIB="$LTHREAD_LIBS -lposix4")])])

Cheers
Vince