Fix bogus handling of special keyboard characters everywhere else. Textfields now only accept valid characters, support right-delete.

OpenRA.FileFormats/Exts.cs

@@ -110,7 +110,14 @@ namespace OpenRA
         public static bool HasModifier(this Modifiers k, Modifiers mod)
         {
             return (k & mod) == mod;
-        }
+        }
+		
+		public static bool IsValidInput(this KeyInput key)
+		{
+			return char.IsLetter(key.UnicodeChar) || char.IsDigit(key.UnicodeChar) || 
+					char.IsSymbol(key.UnicodeChar) || char.IsSeparator(key.UnicodeChar) || 
+					char.IsPunctuation(key.UnicodeChar);
+		}
 
         public static V GetOrAdd<K, V>(this Dictionary<K, V> d, K k)
             where V : new()