Implement modification stamp for ScriptInitializer

This should influence ResolveElementCache to correctly update caches
because it rely on modifications stamps of the declaration
Before this change file.modificationStamp was used for script initializers in file, so they all became outdated after some change in file

compiler/psi/src/org/jetbrains/kotlin/psi/KtAnonymousInitializer.kt

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
 import org.jetbrains.kotlin.psi.stubs.KotlinPlaceHolderStub
 import org.jetbrains.kotlin.psi.stubs.elements.KtStubElementTypes
 import org.jetbrains.kotlin.utils.sure
+import java.util.concurrent.atomic.AtomicLong
 
 interface KtAnonymousInitializer : KtDeclaration, KtStatementExpression {
     val containingDeclaration: KtDeclaration
@@ -57,4 +58,15 @@ class KtScriptInitializer(node: ASTNode) : KtDeclarationImpl(node), KtAnonymousI
         get() = getParentOfType<KtScript>(true).sure { "Should only be present in script" }
 
     override fun <R, D> accept(visitor: KtVisitor<R, D>, data: D) = visitor.visitScriptInitializer(this, data)
+
+    private val modificationStamp = AtomicLong()
+
+    override fun subtreeChanged() {
+        super.subtreeChanged()
+        modificationStamp.getAndIncrement()
+    }
+
+    fun getModificationStamp(): Long {
+        return modificationStamp.get()
+    }
 }

compiler/psi/src/org/jetbrains/kotlin/psi/KtElement.kt

@@ -33,6 +33,7 @@ fun KtElement.getModificationStamp(): Long {
         is KtFile -> this.modificationStamp
         is KtDeclarationStub<*> -> this.modificationStamp
         is KtSuperTypeList -> this.modificationStamp
+        is KtScriptInitializer -> this.getModificationStamp()
         else -> (parent as KtElement).getModificationStamp()
     }
 }