sys_select [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]
sys_time [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]
errno [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]
+msvc-nothrow [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]
configure.ac:
gl_FUNC_POLL