Add Coroutines.DEFAULT to Gradle plugin

See CommonCompilerArguments changes

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinProjectExtension.kt

@@ -63,12 +63,11 @@ open class ExperimentalExtension {
 enum class Coroutines {
     ENABLE,
     WARN,
-    ERROR;
+    ERROR,
+    DEFAULT;
 
     companion object {
-        val DEFAULT = WARN
-
         fun byCompilerArgument(argument: String): Coroutines? =
-                Coroutines.values().firstOrNull { it.name.equals(argument, ignoreCase = true) }
+            Coroutines.values().firstOrNull { it.name.equals(argument, ignoreCase = true) }
     }
 }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/tasks/Tasks.kt

@@ -269,6 +269,7 @@ abstract class AbstractKotlinCompile<T : CommonCompilerArguments>() : AbstractKo
             Coroutines.ENABLE -> CommonCompilerArguments.ENABLE
             Coroutines.WARN -> CommonCompilerArguments.WARN
             Coroutines.ERROR -> CommonCompilerArguments.ERROR
+            Coroutines.DEFAULT -> CommonCompilerArguments.DEFAULT
         }
 
         logger.kotlinDebug { "args.coroutinesState=${args.coroutinesState}" }