Move JvmTarget to frontend.java, introduce TargetPlatformVersion

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

compiler/frontend/src/org/jetbrains/kotlin/analyzer/AnalyzerFacade.kt

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.builtins.DefaultBuiltIns
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.config.LanguageVersionSettingsImpl
+import org.jetbrains.kotlin.config.TargetPlatformVersion
 import org.jetbrains.kotlin.container.ComponentProvider
 import org.jetbrains.kotlin.context.ModuleContext
 import org.jetbrains.kotlin.context.ProjectContext
@@ -37,7 +38,6 @@ import org.jetbrains.kotlin.resolve.CompilerEnvironment
 import org.jetbrains.kotlin.resolve.MultiTargetPlatform
 import org.jetbrains.kotlin.resolve.TargetEnvironment
 import org.jetbrains.kotlin.resolve.TargetPlatform
-import org.jetbrains.kotlin.utils.DescriptionAware
 import org.jetbrains.kotlin.utils.singletonOrEmptyList
 import java.util.*
 
@@ -261,15 +261,15 @@ private class DelegatingPackageFragmentProvider(
 interface LanguageSettingsProvider {
     fun getLanguageVersionSettings(moduleInfo: ModuleInfo, project: Project): LanguageVersionSettings
 
-    fun getTargetPlatform(moduleInfo: ModuleInfo): DescriptionAware
+    fun getTargetPlatform(moduleInfo: ModuleInfo): TargetPlatformVersion
 
     object Default : LanguageSettingsProvider {
         override fun getLanguageVersionSettings(moduleInfo: ModuleInfo, project: Project) = LanguageVersionSettingsImpl.DEFAULT
 
-        override fun getTargetPlatform(moduleInfo: ModuleInfo): DescriptionAware = DescriptionAware.NoVersion
+        override fun getTargetPlatform(moduleInfo: ModuleInfo): TargetPlatformVersion = TargetPlatformVersion.NoVersion
     }
 
     companion object {
         fun getInstance(project: Project) = ServiceManager.getService(project, LanguageSettingsProvider::class.java) ?: Default
     }
-}
+}