Increase tex2lyx output format to 378.

Increase tex2lyx output format to 378.
369: Nothing to do (empty lyx2lyx conversion)
370: Nothing to do (empty lyx2lyx conversion)
371: Added \use_mhchem parameter
372: Nothing to do (empty lyx2lyx conversion)
373: Nothing to do (the old version was wrong since it used the new g-brief
     layout files with the old file format)
374: Nothing to do (html output changes)
375: Nothing to do (empty lyx2lyx conversion)
376: Nothing to do (empty lyx2lyx conversion)
377: Nothing to do (empty lyx2lyx conversion)
378: Nothing to do (empty lyx2lyx conversion)

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@39911 a592a061-630c-0410-9148-cb99ea01b6c8