Allow configuration of the character appended in case of a nick

conflict.

src/common/config.py

@@ -92,6 +92,7 @@ class Config:
 		'gc-height': [opt_int, 400],
 		'gc-hpaned-position': [opt_int, 540],
 		'gc_refer_to_nick_char': [opt_str, ','],
+		'gc_proposed_nick_char': [opt_str, '_'],
 		'chat-x-position': [opt_int, 0],
 		'chat-y-position': [opt_int, 0],
 		'chat-width': [opt_int, 480],

src/common/connection.py

@@ -456,7 +456,8 @@ class Connection:
 				elif errcode == '409': # nick conflict
 					# the jid_from in this case is FAKE JID: room_jid/nick
 					# resource holds the bad nick so propose a new one
-					proposed_nickname = resource + '_'
+					proposed_nickname = resource + \
+						gajim.config.get('gc_proposed_nick_char')
 					room_jid = gajim.get_room_from_fjid(who)
 					self.dispatch('ASK_NEW_NICK', (room_jid, _('Unable to join room'), 
 		_('Your desired nickname is in use or registered by another occupant.\nPlease specify another nickname below:'), proposed_nickname))