updated for version 7.3.1292
Problem:    Possibly using invalid pointer when searcing for window. (Raichoo)
Solution:   Use "firstwin" instead of "tp_firstwin" for current tab.
Added tag v7-3-1292 for changeset cad8d29b0bc0
updated for version 7.3.1293
Problem:    Put in empty buffer cannot be undone.
Solution:   Save one more line for undo. (Ozaki)
Added tag v7-3-1293 for changeset 18b43970fb7a