Previously JvmTarget was declared in module 'util' which is accessible
for example from 'frontend', which is not very good.
Also add a superinterface named TargetPlatformVersion which is going to
be used in platform-independent injectors in 'frontend' in the following
commits. Use it in one place (LanguageVersionSettingsProviderImpl.kt)
instead of DescriptionAware because TargetPlatformVersion sounds like a
better abstraction than DescriptionAware here
Alexander Udalov
573c6ab5d4