os: drop special case for FreeBSD 10.4 in newFile

Support for FreeBSD 10 will be dropped with Go 1.13, so revert the
workaround introduced in CL 157099.

Updates #29633
Updates #27619

Change-Id: I1a2e50d3f807a411389f3db07c0f4535a590da02
Reviewed-on: https://go-review.googlesource.com/c/go/+/165801
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/os/file_unix.go

@@ -123,15 +123,7 @@ func newFile(fd uintptr, name string, kind newFileKind) *File {
 	if kind == kindOpenFile {
 		var st syscall.Stat_t
 		switch runtime.GOOS {
-		case "freebsd":
-			// On FreeBSD before 10.4 it used to crash the
-			// system unpredictably while running all.bash.
-			// When we stop supporting FreeBSD 10 we can merge
-			// this into the dragonfly/netbsd/openbsd case.
-			// Issue 27619.
-			pollable = false
-
-		case "dragonfly", "netbsd", "openbsd":
+		case "dragonfly", "freebsd", "netbsd", "openbsd":
 			// Don't try to use kqueue with regular files on *BSDs.
 			// On FreeBSD a regular file is always
 			// reported as ready for writing.