add conflict resolution

var _code: Int { get } 
from CustomNSError and RawRepresentable 
conflict with each other

Author: zayass

Foundation/NSError.swift

@@ -296,13 +296,23 @@ extension CustomNSError where Self: RawRepresentable, Self.RawValue: SignedInteg
     public var errorCode: Int {
         return numericCast(self.rawValue)
     }
+    
+    // conflict resolution
+	var _code: Int {
+		return errorCode
+	}
 }
 
 extension CustomNSError where Self: RawRepresentable, Self.RawValue: UnsignedInteger {
     // The error code of Error with integral raw values is the raw value.
     public var errorCode: Int {
         return numericCast(self.rawValue)
     }
+    
+    // conflict resolution
+	var _code: Int {
+		return errorCode
+	}
 }
 
 public extension Error where Self : CustomNSError {