The LFUN buffer-reset-export states to start afresh the export for the
next run, but in fact, the boolean was never reset, so that this was
done for all subsequent runs unless the buffer had been closed and
reopened.
Now the lfun does what it states and only acts on the next pass.
(cherry picked from commit e1cb15ee5d)
The code that handles this special macro insertion (in
Cursor::mathMacroClose())) is very weird: it inserts the contents of
the macro _after_ the macro and later, since the macro is 'greedy', it
will eat this contents and put it in its first macro cell.
Does it make sense to you? It does not ake sense to me either. Anyway,
this is the point where one should make sure that the buffer is set.
Fixes ticket #12682.
(cherry picked from commit b45a957929)
