Change function declarations and definitions related to sigvec.

Addressed upstream with the removal of sigvec in this commit:

commit 0781a7772ae1385fe8d7a734fdb35df81b1e6590

Author: Roland McGrath <roland@hack.frob.com>

Date:   Fri Nov 14 10:52:16 2014 -0800

    Remove sigvec.

diff --git a/include/signal.h b/include/signal.h

index a019395882176073..d9f279c9bf0aca3d 100644

--- a/include/signal.h

+++ b/include/signal.h

@@ -40,6 +40,7 @@ extern int __sigtimedwait (const sigset_t *__set, siginfo_t *__info,

 libc_hidden_proto (__sigtimedwait)

 extern int __sigqueue (__pid_t __pid, int __sig,

 		       const union sigval __val);

+struct sigvec;

 extern int __sigvec (int __sig, const struct sigvec *__vec,

 		     struct sigvec *__ovec);

 extern int __sigreturn (struct sigcontext *__scp);

diff --git a/signal/sigvec.c b/signal/sigvec.c

index e44daf1ab6fd2f39..21e304d944e46c18 100644

--- a/signal/sigvec.c

+++ b/signal/sigvec.c

@@ -24,10 +24,7 @@

    reset to SIG_DFL before `sv_handler' is entered.  If OVEC is non-NULL,

    it is filled in with the old information for SIG.  */

 int

-__sigvec (sig, vec, ovec)

-     int sig;

-     const struct sigvec *vec;

-     struct sigvec *ovec;

+__sigvec (int sig, const struct sigvec *vec, struct sigvec *ovec)

 {

   __set_errno (ENOSYS);

   return -1;

diff --git a/sysdeps/posix/sigvec.c b/sysdeps/posix/sigvec.c

index 89e3d44d88ce3ee5..6a3ccc8eaf8ae0a5 100644

--- a/sysdeps/posix/sigvec.c

+++ b/sysdeps/posix/sigvec.c

@@ -43,10 +43,7 @@ static struct sigvec_wrapper_data sigvec_wrapper_data[NSIG];

    reset to SIG_DFL before `sv_handler' is entered.  If OVEC is non-NULL,

    it is filled in with the old information for SIG.  */

 int

-__sigvec (sig, vec, ovec)

-     int sig;

-     const struct sigvec *vec;

-     struct sigvec *ovec;

+__sigvec (int sig, const struct sigvec *vec, struct sigvec *ovec)

 {

   struct sigaction old;

@@ -159,8 +156,7 @@ weak_alias (__sigvec, sigvec)

 #ifndef SA_RESETHAND

 static void

-sigvec_wrapper_handler (sig)

-     int sig;

+sigvec_wrapper_handler (int sig)

 {

   struct sigvec_wrapper_data *data;

   struct sigaction act;