This reverts commit 6271f5cbe5.
The original commit 15094eb03a was reverted because it caused a problem
during bootstrap. That problem is fixed in a subsequent commit.
After a generation of fake overrides some code may still to refer old
symbols from declaration storage (like computation of overridden
symbols for lazy functions), so we need to remap those symbols using
information from IR f/o generator
Alexander Udalov