syscalls -- Add sys_sigaltstack

Will need it to retrieve signal stack parameters.
Note for simplicty I declared the syscall having
void * arguments, while libc has it as stack_t *.
This need to be cleaned up one day (because
we use similar structure for sigframe definition
and need to merge both definitions down).

ARM syscall def from alekskartashov@
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

arch/arm/syscall.def

@@ -63,6 +63,7 @@ capset				126	185	(struct cap_header *h, struct cap_data *d)
 rt_sigqueueinfo			129     178	(pid_t pid, int sig, siginfo_t *info)
 setpriority			141	97	(int which, int who, int nice)
 sched_setscheduler		144	156	(int pid, int policy, struct sched_param *p)
+sigaltstack			131	186	(const void *uss, void *uoss)
 personality			135	136	(unsigned int personality)
 prctl				157	172	(int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5)
 arch_prctl			158	17	(int option, unsigned long addr)

arch/x86/syscall-x86-64.def

@@ -61,6 +61,7 @@ __NR_setfsgid		123		sys_setfsgid		(int fsgid)
 __NR_getsid		124		sys_getsid		(void)
 __NR_capset		126		sys_capset		(struct cap_header *h, struct cap_data *d)
 __NR_rt_sigqueueinfo	129		sys_rt_sigqueueinfo	(pid_t pid, int sig, siginfo_t *info)
+__NR_sigaltstack	131		sys_sigaltstack		(const void *uss, void *uoss)
 __NR_personality	135		sys_personality		(unsigned int personality)
 __NR_setpriority	141		sys_setpriority		(int which, int who, int nice)
 __NR_sched_setscheduler	144		sys_sched_setscheduler	(int pid, int policy, struct sched_param *p)