RFR 8203369 : Check for both EAGAIN and EWOULDBLOCK error codes

[Ivan Gerasimov]

Hello!

On Unix systems several system calls (including pread, read, readv, 
recvfrom, recvmsg, send, sendfile, sendmsg, sendto) may set errno to 
either EAGAIN or EWOULDBLOCK on the same condition.

On Linux these two constants are the same, but they are not required to 
be the same.

For example, here's an extract from the Linux man page of send():
EAGAIN or EWOULDBLOCK
The  socket  is marked nonblocking and the requested operation would 
block.  POSIX.1-2001 allows either error to be returned for this case, 
and does not require these constants to have the same value, so a 
portable application should check for both possibilities.

We should check for both error codes when appropriate.

Would you please help review the fix?

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8203369
WEBREV: http://cr.openjdk.java.net/~igerasim/8203369/00/webrev/

Thanks!

-- 
With kind regards,
Ivan Gerasimov