Split get_oom_base message in two functions
* src/oomhelp.cpp (get_oom_base_message_from_mapi): New. (get_oom_message): Obtain the Mapi message from a Mail item. (get_oom_base_message): Use both functions to do the same as before. * src/oomhelp.h: Update accordingly.
The conversion from MailItem to MAPI Message is useful
in itself. E.g. in a normal read event.