Initially, the system is frozen with an Ace file using no precompiled
library that specifies either `multithreaded (yes)' or
`shared_library_definition ("/foo/bar")'.  Then the Ace file is
changed to indicate `multithreaded (no)' or to delete the line with
the shared_library_definition specification and the system is
refrozen.  The compiled C code is not removed first, so it the
non-multithreaded code won't link.

Discovered in Release 5.0.016.