btr0cur.c: Undo changes to white space that make the code differ from
branches/zip.

btr_cur_del_unmark_for_ibuf(): Remove this unused function.

btr_cur_set_deleted_flag_for_ibuf(): Add missing UNIV_INTERN specifier.
Correct the function comment.  Call btr_rec_set_deleted_flag() instead
of rec_set_deleted_flag_new(), so that delete buffering will actually
work on ROW_FORMAT=REDUNDANT tables.