axfer: allow to be compiled with glibc-2.11 or former

axfer: allow to be compiled with glibc-2.11 or former

The program, axfer, was developed in userspace with glibc-2.28. This
userspace is mostly compliant to POSIX:2008 and some additional macros
for poll event are officially available. The glibc supports them as a
default since its v2.12 release. It will be failed to be compiled with
old glibc or the other libraries for C standard APIs.

One of the purpose of axfer is an better alternative of aplay. In a
point of the purpose, it's preferable to be compiled with the old
libraries.

This commit adds conditional macros to be compiled with libraries for
old compliance level of POSIX.

Reported-by: Jay Foster <jay@systech.com>
Fixes: fce16d9279b6 ('axfer: add an implementation of waiter for select(2)')
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>