Fix MapiHelper
Fix MapiHelper

On Windows 10 the default is to use Unicode. Trying to send emails
with the Ansi API fails for some email providers, e.g. Outlook.
This change adds support for Unicode for Windows versions > 8.

gmartin7/libpalaso,ermshiperete/libpalaso,gmartin7/libpalaso,ermshiperete/libpalaso,sillsdev/libpalaso,sillsdev/libpalaso,gmartin7/libpalaso,ermshiperete/libpalaso,ermshiperete/libpalaso,sillsdev/libpalaso,sillsdev/libpalaso,gmartin7/libpalaso