Cut out code duplication in impersonators for boxes & procedures
Attach vector_set and vector_ref labels to relevant vector types
Impersonator properties and some simple cleanups
Add some assertions
Add some stub predicates and weak boxes
Add placeholders and ephemerons
Fix type error
Implement weak boxes and ephemerons using weak references
More stubs
Merge branch 'master' into structs
complex? is true for all numbers.
Symbol additions.
Fix translation errors.
Add a lot of stubbed predicates.

Also, error on duplicate expose calls.
Make synthesized continuations have the proper fields.
Handle w-c-m as top frame.
Add parameterizations, fix cms-first for #f first arg.
More stubs.
Merge branch 'master' into structs