Java to Kotlin converter: better comments preserving, never lose any comment

#KT-4489 Fixed

j2k/tests/testData/ast/comments/comments2.java

@@ -0,0 +1,20 @@
+//file
+package foo;
+
+class A {
+    void/* nothing to return */ foo(/* no parameters at all */) {
+        // let declare a variable
+        // with 2 comments before
+        int/*int*/ a /* it's a */ = 2 /* it's 2 */ + 1 /* it's 1 */; // variable a declared
+    } // end of foo
+
+    int/* we return int*/ foo(int/*int*/ p/* parameter p */) { /* body is empty */ }
+
+    private/*it's private*/ int field = 0;
+
+    public /*it's public*/ char foo() { }
+
+    protected/*it's protected*/ void foo() { }
+
+    public/*it's public*/ static/*and static*/ final/*and final*/ int C = 1;
+}