unix: add Poll function on Solaris

Tested with TestPoll extracted from syscall_linux_test.go.

Now that Poll is supported on all unix flavors, TestPoll can be moved
to syscall_unix_test.go in a successive CL.

Change-Id: Ibd5ff3f45198008464522c3b165f2af7865ce81e
Reviewed-on: https://go-review.googlesource.com/73881
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/zsyscall_solaris_amd64.go

@@ -29,6 +29,7 @@ import (
 //go:cgo_import_dynamic libc___major __major "libc.so"
 //go:cgo_import_dynamic libc___minor __minor "libc.so"
 //go:cgo_import_dynamic libc_ioctl ioctl "libc.so"
+//go:cgo_import_dynamic libc_poll poll "libc.so"
 //go:cgo_import_dynamic libc_access access "libc.so"
 //go:cgo_import_dynamic libc_adjtime adjtime "libc.so"
 //go:cgo_import_dynamic libc_chdir chdir "libc.so"
@@ -153,6 +154,7 @@ import (
 //go:linkname proc__major libc___major
 //go:linkname proc__minor libc___minor
 //go:linkname procioctl libc_ioctl
+//go:linkname procpoll libc_poll
 //go:linkname procAccess libc_access
 //go:linkname procAdjtime libc_adjtime
 //go:linkname procChdir libc_chdir
@@ -278,6 +280,7 @@ var (
 	proc__major,
 	proc__minor,
 	procioctl,
+	procpoll,
 	procAccess,
 	procAdjtime,
 	procChdir,
@@ -557,6 +560,15 @@ func ioctl(fd int, req uint, arg uintptr) (err error) {
 	return
 }
 
+func poll(fds *PollFd, nfds int, timeout int) (n int, err error) {
+	r0, _, e1 := sysvicall6(uintptr(unsafe.Pointer(&procpoll)), 3, uintptr(unsafe.Pointer(fds)), uintptr(nfds), uintptr(timeout), 0, 0, 0)
+	n = int(r0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
 func Access(path string, mode uint32) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(path)