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/sigcontextinfo.h

@@ -0,0 +1,24 @@
+/* Copyright (C) 1999-2014 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/>.  */
+
+#define SIGCONTEXT int _code, struct sigcontext *
+#define SIGCONTEXT_EXTRA_ARGS _code,
+#define GET_PC(ctx)	((void *) (ctx)->sc_pc)
+#define GET_FRAME(ctx)	((void *) (ctx)->sc_regs[15])
+#define GET_STACK(ctx)	((void *) (ctx)->sc_regs[30])
+#define CALL_SIGHANDLER(handler, signo, ctx) \
+  (handler)((signo), SIGCONTEXT_EXTRA_ARGS (ctx))