Support fun interfaces in kotlinx-metadata

#KT-37421 Fixed

libraries/kotlinx-metadata/jvm/ChangeLog.md

@@ -1,5 +1,10 @@
 # kotlinx-metadata-jvm
 
+## 0.1.1
+
+- [`KT-37421`](https://youtrack.jetbrains.com/issue/KT-37421) Add Flag.Class.IS_FUN for functional interfaces
+- Add `KmModule.optionalAnnotationClasses` for the new scheme of compilation of OptionalExpectation annotations in multiplatform projects ([KT-38652](https://youtrack.jetbrains.com/issue/KT-38652))
+
 ## 0.1.0
 
 - [`KT-26602`](https://youtrack.jetbrains.com/issue/KT-26602) Provide a value-based API

libraries/kotlinx-metadata/src/kotlinx/metadata/Flag.kt

@@ -207,6 +207,12 @@ class Flag(private val offset: Int, private val bitWidth: Int, private val value
          */
         @JvmField
         val IS_INLINE = Flag(F.IS_INLINE_CLASS)
+
+        /**
+         * Signifies that the corresponding class is a functional interface, i.e. marked with the keyword `fun`.
+         */
+        @JvmField
+        val IS_FUN = Flag(F.IS_FUN_INTERFACE)
     }
 
     /**