Fix bug in type checker

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

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add more builtin constants

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Simplify how universe variable constraints are represented in the kernel. Allow universe variable to be created without an environment.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Fix test failure when using clang++ and release mode

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Add basic definitions and axioms

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