Get rid of 'class object' usages in code and builtins

Replace some comments and library usages as well

compiler/backend/src/org/jetbrains/kotlin/codegen/PlatformStaticGenerator.kt

@@ -76,7 +76,7 @@ class PlatformStaticGenerator(
         )
     }
 
-    class object {
+    companion object {
         [platformStatic]
         public fun createStaticFunctionDescriptor(descriptor: FunctionDescriptor): FunctionDescriptor {
             val memberDescriptor = if (descriptor is PropertyAccessorDescriptor) descriptor.getCorrespondingProperty() else descriptor

compiler/backend/src/org/jetbrains/kotlin/codegen/SourceInfo.kt

@@ -24,7 +24,7 @@ import org.jetbrains.kotlin.psi.JetNamedFunction
 
 data public class SourceInfo(val source: String, val pathOrCleanFQN: String, val linesInFile: Int) {
 
-    class object {
+    companion object {
         fun createInfo(element: JetElement?, internalClassName: String): SourceInfo {
             assert(element != null) { "Couldn't create source mapper for null element " + internalClassName }
             val lineNumbers = CodegenUtil.getLineNumberForElement(element!!.getContainingFile(), true)

compiler/backend/src/org/jetbrains/kotlin/codegen/extensions/ExpressionCodegenExtension.kt

@@ -28,7 +28,7 @@ import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.resolve.*
 
 public trait ExpressionCodegenExtension {
-    class object : ProjectExtensionDescriptor<ExpressionCodegenExtension>("org.jetbrains.kotlin.expressionCodegenExtension", javaClass<ExpressionCodegenExtension>())
+    companion object : ProjectExtensionDescriptor<ExpressionCodegenExtension>("org.jetbrains.kotlin.expressionCodegenExtension", javaClass<ExpressionCodegenExtension>())
 
     public class Context(
             public val typeMapper: JetTypeMapper,

compiler/backend/src/org/jetbrains/kotlin/codegen/inline/ReifiedTypeInliner.kt

@@ -34,7 +34,7 @@ import org.jetbrains.kotlin.resolve.DescriptorUtils
 
 public class ReifiedTypeInliner(private val parametersMapping: ReifiedTypeParameterMappings?) {
 
-    class object {
+    companion object {
         public val NEW_ARRAY_MARKER_METHOD_NAME: String = "reifyNewArray"
         public val CHECKCAST_MARKER_METHOD_NAME: String = "reifyCheckcast"
         public val INSTANCEOF_MARKER_METHOD_NAME: String = "reifyInstanceof"

compiler/backend/src/org/jetbrains/kotlin/codegen/inline/SMAP.kt

@@ -143,7 +143,7 @@ trait SourceMapper {
         parent?.visitOrigin()
     }
 
-    class object {
+    companion object {
 
         fun flushToClassBuilder(mapper: SourceMapper, v: ClassBuilder) {
             for (fileMapping in mapper.resultMappings) {
@@ -253,7 +253,7 @@ class SMAP(val fileMappings: List<FileMapping>) {
         sourceInfo = SourceInfo(default.name, default.path, defaultMapping.source + defaultMapping.range - 1)
     }
 
-    class object {
+    companion object {
         val FILE_SECTION = "*F"
 
         val LINE_SECTION = "*L"