Add scanner base class

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add instantiate tests

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Rename abst_type to abst_domain

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add (relaxed) version of instantiate that can substitute terms containing free variables

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Flip order of the arguments for instance and abstract. Simplify type_checker.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Remove dead code

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Rename (stack) value to svalue

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add support for semantic attachments. Remove expr_numeral

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>