iphlpapi: For platforms that do not implement /proc, return Unimplemented for the functions trying to read from there.

advapi32: Print out the unknown value for sid use in the LookupAccountName test, instead of the known value.

comctl32: Don't set the focus to the text box when the ComboBoxEx receives a CBN_SELENDCANCEL notification.

credui: The pUIInfo parameter is optional to CredUIPromptForCredentials, so check before dereferencing it to get the parent window.