server: Move most of the duplicate_token request to a new function, token_duplicate, to enable the code to be used inside wineserver.

urlmon: There is no need to make slash conversion in BindToStorage as URL is already canonized in the constructor.

Use it to implement the behaviour where InternetReadFileExA does a 
synchronous request if the data is available and asynchronous otherwise.

wininet: Don't close the connection if the caller passes in zero for the number of bytes to be read.

Only close the connection when the bytes read equals the content length.

Fixup HTTP_DrainContent, which relied on the previous incorrect 
behaviour to instead close connections with no content length manually.

wininet: Fix basic authentication by putting Basic directing into the scheme field, as the pszAuthValue can have an optional realm string appended.

shell32/tests: With recent PSDKs, CSIDL_MYDOCUMENTS is a synonym for CSIDL_PERSONAL. So define our own constant.