add isIncremental method to PackageFragmentDescriptorImpl in order to recognize descriptors from incremental package fragments during compilation

compiler/frontend.java/src/org/jetbrains/kotlin/load/kotlin/incremental/IncrementalPackageFragmentProvider.kt

@@ -134,6 +134,8 @@ public class IncrementalPackageFragmentProvider(
 
         override fun getMemberScope(): JetScope = memberScope()
 
+        override fun isIncremental(): Boolean = true
+
         private inner class IncrementalPackageScope(val packageData: PackageData) : DeserializedPackageMemberScope(
                 this@IncrementalPackageFragment, packageData.packageProto, packageData.nameResolver, deserializationComponents,
                 { listOf() }

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/PackageFragmentDescriptorImpl.kt

@@ -40,4 +40,7 @@ public abstract class PackageFragmentDescriptorImpl(
     }
 
     override fun toString(): String = "package $fqName"
+
+    @Deprecated("This is a hack in order to preliminary support internal visibility in multi-module projects")
+    open fun isIncremental(): Boolean = false
 }