Deprecate monitorEnter and monitorExit not to be used from user code.

libraries/stdlib/src/kotlin/jvm/internal/unsafe/monitor.kt

@@ -20,8 +20,10 @@ import kotlin.jvm.internal.Intrinsic
 
 /** @suppress */
 @Intrinsic("kotlin.jvm.internal.unsafe.monitorEnter")
+@Deprecated("This function supports the standard library infrastructure and is not intended to be used directly from user code.")
 public fun monitorEnter(monitor: Any): Unit = throw UnsupportedOperationException("This function can only be used privately")
 
 /** @suppress */
 @Intrinsic("kotlin.jvm.internal.unsafe.monitorExit")
+@Deprecated("This function supports the standard library infrastructure and is not intended to be used directly from user code.")
 public fun monitorExit(monitor: Any): Unit = throw UnsupportedOperationException("This function can only be used privately")

libraries/stdlib/src/kotlin/util/Synchronized.kt

@@ -8,6 +8,7 @@ import kotlin.jvm.internal.unsafe.*
 /**
  * Executes the given function [block] while holding the monitor of the given object [lock].
  */
+@Suppress("DEPRECATION")
 public inline fun <R> synchronized(lock: Any, block: () -> R): R {
     monitorEnter(lock)
     try {