Add debug documents to SwDBManager::MergeMailFiles
Add debug documents to SwDBManager::MergeMailFiles

Just like the debug documents in SwDBManager::MergeDocuments.

Change-Id: I275575853c80d4e19d6df5ba9d8dc689353d7c85
Reviewed-on: https://gerrit.libreoffice.org/10970
Reviewed-by: Björn Michaelsen <e7b7acdb701579ea6e93eb181deb22e8c89dcb50@canonical.com>
Tested-by: Björn Michaelsen <e7b7acdb701579ea6e93eb181deb22e8c89dcb50@canonical.com>

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core