Fixing select

[Richard Braun]

Hello,

A while ago [1], issues were found with the use of select along with
a timeout. In an attempt to fix those, I have created a branch in the
Hurd repository which adds a new call to the io interface,
io_select_timeout, and adjusts the servers to support this new call.
The core of the implementation lies in the new hurd_condition_timedwait
call, and the consistent use of the new Hurd-specific time_data_t type.
Comments on these changes are welcome.

For now, this branch only adds support for server-side timeouts. The
select implementation in glibc still needs to be changed to use the new
call when appropriate.

THanks.

-- 
Richard Braun

[1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=79358