KT-3949 Extend selection in case of comment before several statements

#KT-3949 Fixed

idea/testData/wordSelection/CommentForStatements/0.kt

@@ -0,0 +1,9 @@
+fun test() {
+    x()
+
+    // <caret>comment for several lines
+    foo()
+    bar()
+
+    y()
+}

idea/testData/wordSelection/CommentForStatements/1.kt

@@ -0,0 +1,9 @@
+fun test() {
+    x()
+
+    // <selection><caret>comment</selection> for several lines
+    foo()
+    bar()
+
+    y()
+}

idea/testData/wordSelection/CommentForStatements/2.kt

@@ -0,0 +1,9 @@
+fun test() {
+    x()
+
+    // <selection><caret>comment for several lines</selection>
+    foo()
+    bar()
+
+    y()
+}

idea/testData/wordSelection/CommentForStatements/3.kt

@@ -0,0 +1,9 @@
+fun test() {
+    x()
+
+    <selection>// <caret>comment for several lines</selection>
+    foo()
+    bar()
+
+    y()
+}

idea/testData/wordSelection/CommentForStatements/4.kt

@@ -0,0 +1,9 @@
+fun test() {
+    x()
+
+<selection>    // <caret>comment for several lines
+</selection>    foo()
+    bar()
+
+    y()
+}

idea/testData/wordSelection/CommentForStatements/5.kt

@@ -0,0 +1,9 @@
+fun test() {
+    x()
+
+<selection>    // <caret>comment for several lines
+    foo()
+    bar()
+</selection>
+    y()
+}

idea/testData/wordSelection/CommentForStatements/6.kt

@@ -0,0 +1,9 @@
+fun test() {
+<selection>    x()
+
+    // <caret>comment for several lines
+    foo()
+    bar()
+
+    y()
+</selection>}