Moved MutableMap.set from Maps.kt to MapsJVM.kt to avoid ambiguity when compile MapTest.kt by JS backend.

libraries/stdlib/src/kotlin/collections/Maps.kt

@@ -12,9 +12,6 @@ public val Map<*, *>.size: Int
 public val Map<*, *>.empty: Boolean
     get() = isEmpty()
 
-/** Provides [] access to maps */
-public fun <K, V> MutableMap<K, V>.set(key: K, value: V): V? = this.put(key, value)
-
 /** Returns the [[Map]] if its not null otherwise it returns the empty [[Map]] */
 public fun <K,V> Map<K,V>?.orEmpty() : Map<K,V>
        = if (this != null) this else stdlib_emptyMap()

libraries/stdlib/src/kotlin/collections/MapsJVM.kt

@@ -8,6 +8,10 @@ import java.util.Properties
 
 // Map APIs
 
+// Move back to Maps.kt after KT-2093 will be fixed
+/** Provides [] access to maps */
+public fun <K, V> MutableMap<K, V>.set(key: K, value: V): V? = this.put(key, value)
+
 /**
  * Converts this [[Map]] to a [[LinkedHashMap]] so future insertion orders are maintained
  */