fix(kernel/expr): old comment

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(util/rb_tree): missing const

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(kernel): add global levels to environment

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/kernel_bindings): add new global level methods to environment Lua API

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(kernel/level): predicate is_param_core

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/kernel_bindings): global level constructor/accessor/recognizer

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/kernel_bindings): add optional arguments to empty_environment Lua API

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(util): name_generator Lua API

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(util): name_set Lua API

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/kernel_bindings): type_checker Lua API

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