This patch (by Wouter van Heyst) fixes compilation of python2.5 on the Hurd (and other systems?)

It fixes the following build error:

gcc -fPIC -fno-strict-aliasing -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -I. -I/build/buildd/python2.5-2.5/./Include -I../Include -I. -I/build/buildd/python2.5-2.5/Include -I/build/buildd/python2.5-2.5/build-static -c /build/buildd/python2.5-2.5/Modules/selectmodule.c -o build/temp.gnu-0.3-i686-AT386-2.5/build/buildd/python2.5-2.5/Modules/selectmodule.o
/build/buildd/python2.5-2.5/Modules/selectmodule.c:676: error: 'select_poll' undeclared here (not in a function)
/build/buildd/python2.5-2.5/Modules/selectmodule.c:676: error: 'poll_doc' undeclared here (not in a function)
/build/buildd/python2.5-2.5/Modules/selectmodule.c: In function 'initselect':
/build/buildd/python2.5-2.5/Modules/selectmodule.c:709: error: 'poll_Type' undeclared (first use in this function)
/build/buildd/python2.5-2.5/Modules/selectmodule.c:709: error: (Each undeclared identifier is reported only once
/build/buildd/python2.5-2.5/Modules/selectmodule.c:709: error: for each function it appears in.)
/build/buildd/python2.5-2.5/Modules/selectmodule.c:709: error: request for member 'ob_type' in something not a structure or union
/build/buildd/python2.5-2.5/Modules/selectmodule.c:709: warning: statement with no effect

We hope this does not break other platforms, does this look OK?