move all error things to new qerr package, replacing errorcodes

qerr/quic_error.go

@@ -0,0 +1,30 @@
+package qerr
+
+import (
+	"fmt"
+)
+
+// ErrorCode can be used as a normal error without reason.
+type ErrorCode uint32
+
+func (e ErrorCode) Error() string {
+	return e.String()
+}
+
+// A QuicError consists of an error code plus a error reason
+type QuicError struct {
+	ErrorCode    ErrorCode
+	ErrorMessage string
+}
+
+// Error creates a new QuicError instance
+func Error(errorCode ErrorCode, errorMessage string) *QuicError {
+	return &QuicError{
+		ErrorCode:    errorCode,
+		ErrorMessage: errorMessage,
+	}
+}
+
+func (e *QuicError) Error() string {
+	return fmt.Sprintf("%s: %s", e.ErrorCode.String(), e.ErrorMessage)
+}