Add test on bytecode text

Test data should be a Kotlin source file with zero or more comments e.g. of
the form: '// 1 INVOKEVIRTUAL'. The test then checks that the generated
bytecode for this file contains exactly one occurrence of the string
'INVOKEVIRTUAL'

compiler/testData/codegen/bytecodeText/privateDefaultArgs.kt

@@ -0,0 +1,16 @@
+// Check that this code doesn't contains INVOKEVIRTUAL instruction
+class B {
+    private fun foo(i: Int = 1) {
+    }
+
+    fun f() {
+       foo(2)
+    }
+}
+
+fun box(): String {
+    return "OK"
+}
+
+// 0 INVOKEVIRTUAL
+// 3 INVOKESPECIAL