Support the "Registrar WHOIS Server" key name for the referral

The ICANN “Registry Registration Data Directory Services
Consistent Labeling and Display Policy” [1] renames the key
from "WHOIS Server" to this.

Remove duplicate "whois server" entry, as noticed by @devl00p

Fixes joepie91#131

[1] https://www.icann.org/resources/pages/rdds-labeling-policy-2017-02-01-en

Author: Ángel González

pythonwhois/net.py

@@ -77,7 +77,7 @@ def get_whois_raw(domain, server="", previous=None, rfc3490=True, never_cut=Fals
 	# Ignore redirects from registries who publish the registrar data themselves
 	if target_server not in ('whois.nic.xyz',):
 		for line in [x.strip() for x in response.splitlines()]:
-			match = re.match("(refer|whois server|referral url|whois server|registrar whois):\s*([^\s]+\.[^\s]+)", line, re.IGNORECASE)
+			match = re.match("(refer|whois server|referral url|registrar whois(?: server)?):\s*([^\s]+\.[^\s]+)", line, re.IGNORECASE)
 			if match is not None:
 				referal_server = match.group(2)
 				if referal_server != server and "://" not in referal_server: # We want to ignore anything non-WHOIS (eg. HTTP) for now.

pythonwhois/parse.py

@@ -156,7 +156,8 @@ def precompile_regexes_dict(source, flags=0):
 					 'Domain Registrar :\s?(?P<val>.+)',
 					 'Registration Service Provider: (?P<val>.+)',
 					 '\tName:\t\s(?P<val>.+)'],
-		'whois_server':		['Whois Server:\s?(?P<val>.+)',
+		'whois_server':		['Registrar WHOIS Server:\s?(?P<val>.+)',
+					 'Whois Server:\s?(?P<val>.+)',
 					 'Registrar Whois:\s?(?P<val>.+)'],
 		'nameservers':		['Name Server:[ ]*(?P<val>[^ ]+)',
 					 'Nameservers:[ ]*(?P<val>[^ ]+)',