Check platform<->impl declaration compatibility

For each platform declaration, there must be at least one impl declaration in
the module with the compatible signature; similarly, for each impl declaration,
there must be at least one platform declaration with the compatible signature.

Note that currently the presence of the 'impl' modifier is not checked yet.

Also, the sad fact is that if you have platform and impl declarations which are
not compatible, you get two errors: on the platform delcaration and on the impl
declaration. This needs to be addressed as well

generators/src/org/jetbrains/kotlin/generators/tests/GenerateTests.kt

@@ -24,6 +24,7 @@ import org.jetbrains.kotlin.android.*
 import org.jetbrains.kotlin.android.configure.AbstractConfigureProjectTest
 import org.jetbrains.kotlin.android.intentions.AbstractAndroidIntentionTest
 import org.jetbrains.kotlin.android.intentions.AbstractAndroidResourceIntentionTest
+import org.jetbrains.kotlin.android.lint.AbstractKotlinLintTest
 import org.jetbrains.kotlin.android.quickfixes.AbstractAndroidQuickFixMultiFileTest
 import org.jetbrains.kotlin.annotation.AbstractAnnotationProcessorBoxTest
 import org.jetbrains.kotlin.annotation.processing.test.sourceRetention.AbstractBytecodeListingTestForSourceRetention
@@ -131,6 +132,7 @@ import org.jetbrains.kotlin.j2k.AbstractJavaToKotlinConverterSingleFileTest
 import org.jetbrains.kotlin.jps.build.*
 import org.jetbrains.kotlin.jps.build.android.AbstractAndroidJpsTestCase
 import org.jetbrains.kotlin.jps.incremental.AbstractProtoComparisonTest
+import org.jetbrains.kotlin.js.test.semantics.*
 import org.jetbrains.kotlin.jvm.compiler.*
 import org.jetbrains.kotlin.jvm.runtime.AbstractJvm8RuntimeDescriptorLoaderTest
 import org.jetbrains.kotlin.jvm.runtime.AbstractJvmRuntimeDescriptorLoaderTest
@@ -139,6 +141,7 @@ import org.jetbrains.kotlin.lang.resolve.android.test.AbstractAndroidBoxTest
 import org.jetbrains.kotlin.lang.resolve.android.test.AbstractAndroidBytecodeShapeTest
 import org.jetbrains.kotlin.lang.resolve.android.test.AbstractAndroidSyntheticPropertyDescriptorTest
 import org.jetbrains.kotlin.modules.xml.AbstractModuleXmlParserTest
+import org.jetbrains.kotlin.multiplatform.AbstractMultiPlatformIntegrationTest
 import org.jetbrains.kotlin.parsing.AbstractParsingTest
 import org.jetbrains.kotlin.psi.patternMatching.AbstractPsiUnifierTest
 import org.jetbrains.kotlin.renderer.AbstractDescriptorRendererTest
@@ -154,8 +157,6 @@ import org.jetbrains.kotlin.serialization.AbstractLocalClassProtoTest
 import org.jetbrains.kotlin.shortenRefs.AbstractShortenRefsTest
 import org.jetbrains.kotlin.test.TargetBackend
 import org.jetbrains.kotlin.types.AbstractTypeBindingTest
-import org.jetbrains.kotlin.android.lint.AbstractKotlinLintTest
-import org.jetbrains.kotlin.js.test.semantics.*
 import java.io.File
 import java.lang.IllegalArgumentException
 import java.util.*
@@ -187,11 +188,14 @@ fun main(args: Array<String>) {
             model("diagnostics/testsWithJsStdLibAndBackendCompilation")
         }
 
-
         testClass<AbstractDiagnosticsWithModifiedMockJdkTest>() {
             model("diagnostics/testWithModifiedMockJdk")
         }
 
+        testClass<AbstractMultiPlatformIntegrationTest>() {
+            model("multiplatform", extension = null, recursive = true, excludeParentDirs = true)
+        }
+
         testClass<AbstractForeignAnnotationsTest>() {
             model("foreignAnnotations/tests")
         }