We are going to deprecate `WITH_RUNTIME` directive. The main reason
behind this change is that `WITH_STDLIB` directive better describes
its meaning, specifically it will add kotlin stdlib to test's classpath.
NB in FE unsigned integer constants are now represented using signed
integer types (e.g., UInt constant actually holds an Int value).
So, in IR so far we also represent unsigned constant literals as
constant values of corresponding signed types, but with corresponding
unsigned type:
0xFFFF_FFFFu becomes 'CONST Int type=kotlin.UInt value=-1'
Ivan Kylchik