Relocate alpha from ports to libc

Also fixed the following whitespace nits to satisfy the push:

sysdeps/alpha/alphaev6/memset.S:142: space before tab in indent.
sysdeps/alpha/configure:1: new blank line at EOF.
sysdeps/alpha/fpu/e_sqrt.c:126: space before tab in indent.
sysdeps/alpha/preconfigure:1: new blank line at EOF.
sysdeps/unix/sysv/linux/alpha/syscalls.list:1: new blank line at EOF.

sysdeps/unix/sysv/linux/alpha/sys/ucontext.h

@@ -0,0 +1,60 @@
+/* Copyright (C) 1998-2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _SYS_UCONTEXT_H
+#define _SYS_UCONTEXT_H	1
+
+#include <features.h>
+#include <signal.h>
+
+#include <bits/sigcontext.h>
+
+
+/* Type for general register.  */
+typedef long int greg_t;
+
+/* Number of general registers.  */
+#define NGREG	33
+
+/* Container for all general registers.  */
+typedef greg_t gregset_t[NGREG];
+
+/* Type for floating-point register.  */
+typedef long int fpreg_t;
+
+/* Number of general registers.  */
+#define NFPREG	32
+
+/* Container for all general registers.  */
+typedef fpreg_t fpregset_t[NFPREG];
+
+
+/* A machine context is exactly a sigcontext.  */
+typedef struct sigcontext mcontext_t;
+
+/* Userlevel context.  */
+typedef struct ucontext
+  {
+    unsigned long int uc_flags;
+    struct ucontext *uc_link;
+    unsigned long __uc_osf_sigmask;
+    stack_t uc_stack;
+    mcontext_t uc_mcontext;
+    __sigset_t uc_sigmask;
+  } ucontext_t;
+
+#endif /* sys/ucontext.h */