There was a code path diversion which prevented blo_red_file_internal
from reading lib blocks from the memory file because it assumed that the
library of objects would remain the same between undos. However, in the
case where we delete the object and there are no other duplicates, the
user count reaches 0 and object_delete_exec will remove the linked
library object from the Context.
This patch removes this code path so that lib blocks are read by the
parser for both file opens and undo/redos.