fastboot: add Socket timeout detection.

UDP fastboot will require re-transmission in the case of datagrams
getting lost. This CL adds Socket functionality to easily distinguish
between a normal timeout and a socket failure.

I also found some Windows docs that indicate sockets may become
invalid after a call to recv() times out. This has never occurred in
my testing, but to be safe this switches the timeout implementation
to use select() instead of SO_RCVTIMEO.

Bug: http://b/26154914
Change-Id: Id7b598f8aea5df1a3676d24702b489042d5f9e3a