Fix for this error:

crosstool-0.28-rc19/build/alpha-unknown-linux-gnu/gcc-3.4.0-glibc-2.3.2/build-glibc/libc_pic.os(.text+0xd9b2c): In function `posix_fallocate64':
: undefined reference to `__GI___pwrite64'
collect2: ld returned 1 exit status
make[1]: *** [crosstool-0.28-rc19/build/alpha-unknown-linux-gnu/gcc-3.4.0-glibc-2.3.2/build-glibc/libc.so] Error 1
make[1]: Leaving directory `crosstool-0.28-rc19/build/alpha-unknown-linux-gnu/gcc-3.4.0-glibc-2.3.2/glibc-2.3.2'
make: *** [all] Error 2

extracted from GLIBC CVS by Dan Kegel
wget 'http://sources.redhat.com/cgi-bin/cvsweb.cgi/libc/sysdeps/unix/sysv/linux/alpha/sysdep.h.diff?r1=1.14&r2=1.15&cvsroot=glibc'
(to match context of...)
wget 'http://sources.redhat.com/cgi-bin/cvsweb.cgi/libc/sysdeps/unix/sysv/linux/alpha/sysdep.h.diff?r1=1.16&r2=1.17&cvsroot=glibc'
and rediffed.

cf. 
http://sources.redhat.com/ml/libc-alpha/2003-10/msg00038.html

Originally thought we needed this hunk, too:
http://sources.redhat.com/ml/libc-alpha/2003-10/msg00037.html
but it seems the sysdep.h change is sufficient, and works better 
when compiling against linux-2.4.

===================================================================
--- glibc-2.3.2/sysdeps/unix/sysv/linux/alpha/sysdep.h.old	2004-05-24 22:21:44.000000000 -0700
+++ glibc-2.3.2/sysdeps/unix/sysv/linux/alpha/sysdep.h	2004-05-24 22:22:48.000000000 -0700
@@ -1,4 +1,4 @@
-/* Copyright (C) 1992, 1993, 1995, 1996, 1997, 2002, 2003
+/* Copyright (C) 1992, 1993, 1995, 1996, 1997, 2002, 2003, 2004
    Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper, <drepper@gnu.ai.mit.edu>, August 1995.
@@ -60,6 +60,21 @@
 #define __NR_osf_getsysinfo	256
 #define __NR_osf_setsysinfo	257
 
+/* Help old kernel headers where particular syscalls are not available.  */
+#ifndef __NR_semtimedop
+# define __NR_semtimedop	423
+#endif
+
+/* This is a kludge to make syscalls.list find these under the names
+   pread and pwrite, since some kernel headers define those names
+   and some define the *64 names for the same system calls.  */
+#if !defined __NR_pread && defined __NR_pread64
+# define __NR_pread __NR_pread64
+#endif
+#if !defined __NR_pwrite && defined __NR_pwrite64
+# define __NR_pwrite __NR_pwrite64
+#endif
+
 /*
  * In order to get the hidden arguments for rt_sigaction set up
  * properly, we need to call the assembly version.  Detect this in the