Change synthetic accessor method names to "access$..."

As per discussion in https://youtrack.jetbrains.com/issue/KT-6870

compiler/testData/codegen/boxWithStdlib/synthetic/syntheticAccessorNames.kt

@@ -0,0 +1,48 @@
+// This test checks that synthetic accessors generated by Kotlin compiler have names starting with "access$"
+// This is crucial for some JVM frameworks like Quasar which rely on the bytecode being similar to the one generated by javac
+// See https://youtrack.jetbrains.com/issue/KT-6870
+
+class PrivateConstructor private() {
+    class Nested { val a = PrivateConstructor() }
+}
+
+class PrivatePropertyGet {
+    private val x = 42
+
+    inner class Inner { val a = x }
+}
+
+class PrivatePropertySet {
+    private var x = "a"
+
+    inner class Inner { { x = "b" } }
+}
+
+class PrivateMethod {
+    private fun foo() = ""
+
+    inner class Inner { val a = foo() }
+}
+
+fun check(klass: Class<*>) {
+    for (method in klass.getDeclaredMethods()) {
+        if (method.isSynthetic() && method.getName().startsWith("access$")) return
+    }
+
+    throw AssertionError("No synthetic methods starting with 'access$' found in class $klass")
+}
+
+fun box(): String {
+    check(javaClass<PrivateConstructor>())
+    check(javaClass<PrivatePropertyGet>())
+    check(javaClass<PrivatePropertySet>())
+    check(javaClass<PrivateMethod>())
+
+    // Also check that synthetic accessors really work
+    PrivateConstructor.Nested()
+    PrivatePropertyGet().Inner()
+    PrivatePropertySet().Inner()
+    PrivateMethod().Inner()
+
+    return "OK"
+}