Compiling `multiprocessing` on OpenBSD fails. `iovec` is not declared.

Adding the following line to multiprocessing.c solves the problem:
#include <sys/uio.h>

But right after I got:
./python:build/lib.openbsd-4.4-amd64-2.6/_multiprocessing.so: undefined
symbol 'sem_timedwait'

It looks like multiprocessing is using a function that is not defined in
OpenBSD and very likely on other BSD's (FreeBSD & NetBSD don't have a
man page for this function)

According to this page, some other systems don't have this function:
http://www.gnu.org/software/gnulib/manual/html_node/sem_005ftimedwait.html

When trying to build Python 2.6 on AIX 5.2 the following error message:

(
 The steps I have taken prior to this are:
  1. export PATH=/usr/bin/:/usr/vacpp/bin/
  2. ./configure --with-gcc=xlc_r --with-cxx=xlC_r --disable-ipv6
  3. make
)

./Modules/ld_so_aix xlc_r -bI:Modules/python.exp build/temp.aix-5.2-
2.6/home/mabr/Python-2.6/Modules/_multiprocessing/multiprocessing.o 
build/temp.aix-5.2-2.6/home/mabr/Python-
2.6/Modules/_multiprocessing/socket_connection.o build/temp.aix-5.2-
2.6/home/mabr/Python-2.6/Modules/_multiprocessing/semaphore.o -
L/usr/local/lib -o build/lib.aix-5.2-2.6/_multiprocessing.so
ld: 0711-317 ERROR: Undefined symbol: .sem_timedwait
ld: 0711-317 ERROR: Undefined symbol: .CMSG_SPACE
ld: 0711-317 ERROR: Undefined symbol: .CMSG_LEN
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more 
information.
*** WARNING: renaming "_multiprocessing" since importing it failed: No 
such file or directory
error: No such file or directory
make: The error code from the last command is 1.

Here is a small patch that lets me build on AIX 5.2.

I confirm build failure on NetBSD 4.0.1 (latest stable) - but
NetBSD-current is - probably - also affected:

*** WARNING: renaming "_multiprocessing" since importing it failed:
build/lib.netbsd-4.0.1-i386-2.6/_multiprocessing.so: Undefined PLT
symbol "sem_timedwait" (symnum = 20)

system: NetBSD 4.0.1 (i386)
Python version: 2.6

Similarly, compile fails on Solaris 9 due to lack of sem_timedwait()
so here is a patch for that.  Solaris 10 was the first Solaris
to have this function so the patch adapts for that case.

Similar to aix-patch, I enclose what I did for compilation
on Solaris 9, using macros from Solaris 10's headers.

These differ slightly to the aix ones, but I don't know if the
difference matters.  (alignment related)