tnef-attachment: Add TNEF part as attachment on error
I thought I'd take a spin with a
-DENABLE_YTNEF build of evolution, but this is all that bought:
ERROR: invalid alloc size 165563 at ytnef.c : 1183, suspected corruption ERROR processing file
-UENABLE_YTNEF build shows the message with an attachment that can be saved, but with
-DENABLE_YTNEF, the attachment is invisible -- no failover to unhandled/saveable winmail.dat file, just poof, gone without a trace.