Improve interop with headers generated by Swift

Support `objc_runtime_name` attribute on Objective-C classes
thus enabling interop with `@objc` Swift classes without
explicitly specified name.

See https://github.com/JetBrains/kotlin-native/issues/1841#issuecomment-411346727

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/ObjCInterop.kt

@@ -5,9 +5,9 @@
 
 package org.jetbrains.kotlin.backend.konan
 
-import org.jetbrains.kotlin.backend.konan.descriptors.findPackage
 import org.jetbrains.kotlin.backend.konan.descriptors.findPackageView
 import org.jetbrains.kotlin.backend.konan.descriptors.getStringValue
+import org.jetbrains.kotlin.backend.konan.descriptors.getStringValueOrNull
 import org.jetbrains.kotlin.backend.konan.irasdescriptors.constructedClass
 import org.jetbrains.kotlin.backend.konan.irasdescriptors.getExternalObjCMethodInfo
 import org.jetbrains.kotlin.backend.konan.irasdescriptors.isReal
@@ -22,7 +22,6 @@ import org.jetbrains.kotlin.resolve.ExternalOverridabilityCondition
 import org.jetbrains.kotlin.resolve.constants.BooleanValue
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.resolve.descriptorUtil.getAllSuperClassifiers
-import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.resolve.descriptorUtil.parentsWithSelf
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeUtils
@@ -229,4 +228,15 @@ fun inferObjCSelector(descriptor: FunctionDescriptor): String = if (descriptor.v
             append(':')
         }
     }
-}
+}
+
+fun ClassDescriptor.getExternalObjCClassBinaryName(): String =
+        this.getExplicitExternalObjCClassBinaryName()
+                ?: this.name.asString()
+
+fun ClassDescriptor.getExternalObjCMetaClassBinaryName(): String =
+        this.getExplicitExternalObjCClassBinaryName()
+                ?: this.name.asString().removeSuffix("Meta")
+
+private fun ClassDescriptor.getExplicitExternalObjCClassBinaryName() =
+        this.annotations.findAnnotation(externalObjCClassFqName)!!.getStringValueOrNull("binaryName")

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/CodeGenerator.kt

@@ -754,7 +754,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
             context.llvm.imports.add(irClass.llvmSymbolOrigin)
 
             if (irClass.isObjCMetaClass()) {
-                val name = irClass.name.asString().removeSuffix("Meta")
+                val name = irClass.descriptor.getExternalObjCMetaClassBinaryName()
 
                 val objCClass = load(codegen.objCDataGenerator!!.genClassRef(name).llvm)
 
@@ -766,7 +766,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
 
                 call(getClass, listOf(objCClass), exceptionHandler = exceptionHandler)
             } else {
-                load(codegen.objCDataGenerator!!.genClassRef(irClass.name.asString()).llvm)
+                load(codegen.objCDataGenerator!!.genClassRef(irClass.descriptor.getExternalObjCClassBinaryName()).llvm)
             }
         } else {
             if (irClass.isObjCMetaClass()) {

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/KotlinObjCClassInfoGenerator.kt

@@ -31,7 +31,7 @@ internal class KotlinObjCClassInfoGenerator(override val context: Context) : Con
 
         val superclassName = irClass.getSuperClassNotAny()!!.let {
             context.llvm.imports.add(it.llvmSymbolOrigin)
-            it.name.asString()
+            it.descriptor.getExternalObjCClassBinaryName()
         }
         val protocolNames = irClass.getSuperInterfaces().map {
             context.llvm.imports.add(it.llvmSymbolOrigin)