Add support for new metavariable representation in the normalizer.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Relax definition of identity_stack. Fix printer for metavariable contexts.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add simplification rule to add_inst

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add simplification to add_lift

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Update todo.md
Add basic support for metavariables at is_convertible. Swap is_convertible arguments to make it more intuitive.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Fix bug in the creation of children environments. Remove unnecessary function.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add support for metavariables in the type checker.

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

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Move src/interval to src/util/interval