core: fix connection to host in child process when socket is non-blocking (with or without proxy)

doc/en/weechat_plugin_api.en.txt

@@ -11758,6 +11758,10 @@ weechat_network_pass_proxy
 
 Establish a connection/authentification to a proxy.
 
+[IMPORTANT]
+This function is blocking on call to connect(), so it must be called in a forked
+process only, to not block WeeChat.
+
 Prototype:
 
 [source,C]
@@ -11801,6 +11805,10 @@ weechat_network_connect_to
 
 Establish a connection to a remote host.
 
+[IMPORTANT]
+This function is blocking on call to connect(), so it must be called in a forked
+process only, to not block WeeChat.
+
 Prototype:
 
 [source,C]

doc/fr/weechat_plugin_api.fr.txt

@@ -11958,6 +11958,10 @@ weechat_network_pass_proxy
 
 Etablit une connexion/authentification avec un proxy.
 
+[IMPORTANT]
+Cette fonction est bloquante sur l'appel à connect(), donc elle doit être
+appelée sans un processus issu d'un "fork", pour ne pas bloquer WeeChat.
+
 Prototype :
 
 [source,C]
@@ -12001,6 +12005,10 @@ weechat_network_connect_to
 
 Etablit une connexion à une machine distante.
 
+[IMPORTANT]
+Cette fonction est bloquante sur l'appel à connect(), donc elle doit être
+appelée sans un processus issu d'un "fork", pour ne pas bloquer WeeChat.
+
 Prototype :
 
 [source,C]

doc/it/weechat_plugin_api.it.txt

@@ -11886,6 +11886,11 @@ weechat_network_pass_proxy
 
 Stabilisce una connessione/autenticazione con un proxy.
 
+[IMPORTANT]
+// TRANSLATION MISSING
+This function is blocking on call to connect(), so it must be called in a forked
+process only, to not block WeeChat.
+
 Prototipo:
 
 [source,C]
@@ -11930,6 +11935,11 @@ weechat_network_connect_to
 
 Stabilisce una connessione con un host remoto.
 
+[IMPORTANT]
+// TRANSLATION MISSING
+This function is blocking on call to connect(), so it must be called in a forked
+process only, to not block WeeChat.
+
 Prototipo:
 
 [source,C]