!133 增加pselect接口实现

Merge pull request !133 from wangchen/pselect_musl

porting/liteos_a/user/src/select/pselect.c

-#include <sys/select.h>
-#include <signal.h>
-#include <stdint.h>
-#include <errno.h>
-#include <unsupported_api.h>
-#include "syscall.h"
-
-#define IS32BIT(x) !((x)+0x80000000ULL>>32)
-#define CLAMP(x) (int)(IS32BIT(x) ? (x) : 0x7fffffffU+((0ULL+(x))>>63))
-
-int pselect(int n, fd_set *restrict rfds, fd_set *restrict wfds, fd_set *restrict efds, const struct timespec *restrict ts, const sigset_t *restrict mask)
-{
-	syscall_arg_t data[2] = { (uintptr_t)mask, _NSIG/8 };
-	time_t s = ts ? ts->tv_sec : 0;
-	long ns = ts ? ts->tv_nsec : 0;
-	unsupported_api(__FUNCTION__);
-#ifdef SYS_pselect6_time64
-	int r = -ENOSYS;
-	if (SYS_pselect6 == SYS_pselect6_time64 || !IS32BIT(s))
-		r = __syscall_cp(SYS_pselect6_time64, n, rfds, wfds, efds,
-			ts ? ((long long[]){s, ns}) : 0, data);
-	if (SYS_pselect6 == SYS_pselect6_time64 || r!=-ENOSYS)
-		return __syscall_ret(r);
-	s = CLAMP(s);
-#endif
-	return syscall_cp(SYS_pselect6, n, rfds, wfds, efds,
-		ts ? ((long[]){s, ns}) : 0, data);
-}