Enable rodex mail account by default and update its docs

Hercules now uses a default packetver that supports RoDEX Account mail,
so it makes sense to enable it.

The comments were also updated with more info about client dates and
flags for RE clients

conf/map/battle/feature.conf

@@ -61,10 +61,9 @@ features: {
 	rodex: true
 
 	// Allow usage of "Account Mail" box in RoDEX?
-	// Requires: 2016-03-16aRagexeRE or later
-	// This is disabled in client-side in some client versions
-	// Disabled by default
-	rodex_use_accountmail: false
+	// Requires: 2016-03-16aRagexeRE (+ patch) or later, 2016-03-23aRagexe or later, any zero client
+	// For RE clients, it requires client patching and you must also uncomment ENABLE_RODEX_ACCOUNT_MAIL_RE_PATCH in src/config/core.h
+	rodex_use_accountmail: true
 
 	// Allow Homunculus autofeeding
 	// true:  enable (Default)