handling of EAGAIN.

This may or may not fix the problem for me (Mandrake 7.2 on a Dell
Optiplex GX110 desktop): I can't hear the output, but it does pass the
test now.  It doesn't fix the problem for Fred (Mandrake 7.2 on a Dell
Inspiron 7500 which has the Maestro sound drivers).  Fred suspects
that it's the kernel version in combination with the driver.