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/bits/sigaction.h

@@ -0,0 +1,75 @@
+/* The proper definitions for Linux/Alpha sigaction.
+   Copyright (C) 1996-2014 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 _SIGNAL_H
+# error "Never include <bits/sigaction.h> directly; use <signal.h> instead."
+#endif
+
+/* Structure describing the action to be taken when a signal arrives.  */
+struct sigaction
+  {
+    /* Signal handler.  */
+#ifdef __USE_POSIX199309
+    union
+      {
+	/* Used if SA_SIGINFO is not set.  */
+	__sighandler_t sa_handler;
+	/* Used if SA_SIGINFO is set.  */
+	void (*sa_sigaction) (int, siginfo_t *, void *);
+      }
+    __sigaction_handler;
+# define sa_handler	__sigaction_handler.sa_handler
+# define sa_sigaction	__sigaction_handler.sa_sigaction
+#else
+    __sighandler_t sa_handler;
+#endif
+
+    /* Additional set of signals to be blocked.  */
+    __sigset_t sa_mask;
+
+    /* Special flags.  */
+    unsigned int sa_flags;
+  };
+
+/* Bits in `sa_flags'.  */
+#define	SA_NOCLDSTOP  0x00000004 /* Don't send SIGCHLD when children stop.  */
+#define SA_NOCLDWAIT  0x00000020 /* Don't create zombie on child death.  */
+#define SA_SIGINFO    0x00000040 /* Invoke signal-catching function with
+				    three arguments instead of one.  */
+#if defined __USE_UNIX98 || defined __USE_MISC
+# define SA_ONSTACK   0x00000001 /* Use signal stack by using `sa_restorer'. */
+#endif
+#if defined __USE_UNIX98 || defined __USE_MISC || defined __USE_XOPEN2K8
+# define SA_RESTART   0x00000002 /* Restart syscall on signal return.  */
+# define SA_NODEFER   0x00000008 /* Don't automatically block the signal
+				    when its handler is being executed.  */
+# define SA_RESETHAND 0x00000010 /* Reset to SIG_DFL on entry to handler.  */
+#endif
+#ifdef __USE_MISC
+# define SA_INTERRUPT 0x20000000 /* Historical no-op.  */
+
+/* Some aliases for the SA_ constants.  */
+# define SA_NOMASK    SA_NODEFER
+# define SA_ONESHOT   SA_RESETHAND
+# define SA_STACK     SA_ONSTACK
+#endif
+
+/* Values for the HOW argument to `sigprocmask'.  */
+#define	SIG_BLOCK     1		 /* Block signals.  */
+#define	SIG_UNBLOCK   2		 /* Unblock signals.  */
+#define	SIG_SETMASK   3		 /* Set the set of blocked signals.  */