Tricket #3761: mcedit: wrong deletion of marked column.
If mark column (Shitf+F3) and select the column from left to right, from
up to down, it can be properly deleted later with F8.
But if select it from right to left, from up to down, erasing with F8
keeps the first line of the selected block.
Solution: don't call eval_marks() several times while deleting vertical
block.
* (edit_block_delete_cmd): calculate mark positions here and pass them...
* (edit_block_delete): ...through here...
* (edit_delete_column_of_text): ...to here.
Signed-off-by: Andrew Borodin <aborodin@vmail.ru>