Relax posix-aio restrictions on newer glibcs

RedHat 9 shipped glibc 2.3.  Modern versions of glibc do not have the aio thread
exit issue that the comment references.  This patch adjusts the check to only
limit aio_init on glibc versions < 2.4.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5304 c046a42c-6fe2-441c-8c8c-71466251a162
