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/setcontext.S

@@ -0,0 +1,34 @@
+/* Install given context.
+   Copyright (C) 2004-2014 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/>.  */
+
+#include <sysdep.h>
+#include <ucontext-offsets.h>
+
+
+/* In case the user fiddled it, copy the "official" signal mask
+   from the ucontext_t into the sigcontext structure.  */
+#undef PSEUDO_PREPARE_ARGS
+#define PSEUDO_PREPARE_ARGS			\
+	ldq	$0, UC_SIGMASK($16);		\
+	stq	$0, UC_SIGCTX+SC_MASK($16);	\
+	lda	$16, UC_SIGCTX($16);
+
+PSEUDO(__setcontext, sigreturn, 1)
+	ret
+PSEUDO_END(__setcontext)
+weak_alias (__setcontext, setcontext)