1. fix a bug that when header contains "Range: 100-", the range request
support will fail
2. (windows) fix a bug that when explorer.exe crashes due to some
reason, the tray icon will disappear.

Send http error

Allow user to display status code errors

This reverts commit 27fe9c8f.

Allows user code to display its own error status responses or just log
the errors. Is called even in cases where begin_request is not called.

update