Fix console cursor on BSDs in async context

`IO.console.cursor` errors on kqueue-based systems when used with the
fiber scheduler.

```ruby
require 'async'

Async { IO.console(:cursor) }.wait
```

This works on Linux but raises `Errno::EINVAL: Invalid argument` with
`IO_Event_Selector_KQueue_Waiting_register` on macOS.

I don't know if it's an acceptable fix, but this patch just dups file
descriptors for stdin/stdout/stderr if detected alongside kqueue.

Author: havenwood

ext/io/console/console.c

@@ -96,6 +96,10 @@ extern VALUE rb_scheduler_timeout(struct timeval *timeout);
 # define rb_fiber_scheduler_make_timeout rb_scheduler_timeout
 #endif
 
+#ifdef HAVE_SYS_EVENT_H
+extern VALUE rb_fiber_scheduler_current(void);
+#endif
+
 #ifndef HAVE_RB_IO_DESCRIPTOR
 static int
 io_descriptor_fallback(VALUE io)
@@ -1695,12 +1699,30 @@ console_dev(int argc, VALUE *argv, VALUE klass)
         int fd;
         VALUE path = rb_obj_freeze(rb_str_new2(CONSOLE_DEVICE));
 
+	fd = -1;
+#ifdef HAVE_SYS_EVENT_H
+	VALUE scheduler = rb_fiber_scheduler_current();
+	if (!NIL_P(scheduler)) {
+		if (isatty(0)) {
+			fd = dup(0);
+			path = rb_obj_freeze(rb_str_new2("<STDIN>"));
+		} else if (isatty(1)) {
+			fd = dup(1);
+			path = rb_obj_freeze(rb_str_new2("<STDOUT>"));
+		} else if (isatty(2)) {
+			fd = dup(2);
+			path = rb_obj_freeze(rb_str_new2("<STDERR>"));
+		}
+	}
+#endif
+	if (fd == -1) {
 #ifdef CONSOLE_DEVICE_FOR_WRITING
-        fd = rb_cloexec_open(CONSOLE_DEVICE_FOR_WRITING, O_RDWR, 0);
-        if (fd < 0) return Qnil;
-        out = rb_io_open_descriptor(klass, fd, FMODE_WRITABLE | FMODE_SYNC, path, Qnil, NULL);
+		int writing_fd = rb_cloexec_open(CONSOLE_DEVICE_FOR_WRITING, O_RDWR, 0);
+		if (writing_fd < 0) return Qnil;
+		out = rb_io_open_descriptor(klass, writing_fd, FMODE_WRITABLE | FMODE_SYNC, path, Qnil, NULL);
 #endif
-        fd = rb_cloexec_open(CONSOLE_DEVICE_FOR_READING, O_RDWR, 0);
+		fd = rb_cloexec_open(CONSOLE_DEVICE_FOR_READING, O_RDWR, 0);
+	}
         if (fd < 0) {
 #ifdef CONSOLE_DEVICE_FOR_WRITING
             rb_io_close(out);

ext/io/console/extconf.rb

@@ -41,6 +41,7 @@
 case ok
 when true
   have_header("sys/ioctl.h") if hdr
+  have_header("sys/event.h")
   # rb_check_hash_type: 1.9.3
   # rb_io_get_write_io: 1.9.1
   # rb_cloexec_open: 2.0.0