asyncio should use signal.set_wakeup_fd on Windows

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-03-31.22:44:55.378>
labels = ['3.7', '3.8', 'type-bug', 'library']
title = 'asyncio should use signal.set_wakeup_fd on Windows'
updated_at = <Date 2018-04-01.23:35:09.554>
user = 'https://github.com/njsmith'

bugs.python.org fields:

activity = <Date 2018-04-01.23:35:09.554>
actor = 'pitrou'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2018-03-31.22:44:55.378>
creator = 'njs'
dependencies = []
files = []
hgrepos = []
issue_num = 33192
keywords = []
message_count = 1.0
messages = ['314749']
nosy_count = 5.0
nosy_names = ['vstinner', 'giampaolo.rodola', 'njs', 'asvetlov', 'yselivanov']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue33192'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']