fix(kernel/inductive): remove unused argument, bug in is_rec_argument (free variable occurrence)

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(kernel): let Pi/Fun also take local constants

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(lua): add example suggested by Cody

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/kernel_bindings): improve Fun/Pi Lua APIs

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