Moved tests

that are used both for codegen & diagnostics to codegen/box/diagnostics

compiler/testData/codegen/box/diagnostics/functions/tailRecursion/realStringEscape.kt

@@ -0,0 +1,16 @@
+fun escapeChar(c : Char) : String? = when (c) {
+    '\\' -> "\\\\"
+    '\n' -> "\\n"
+    '"'  -> "\\\""
+    else -> "" + c
+}
+
+tailRecursive fun String.escape(i : Int = 0, result : StringBuilder = StringBuilder()) : String =
+        if (i == length) result.toString()
+        else escape(i + 1, result.append(escapeChar(get(i))))
+
+fun box() : String {
+    "test me not \\".escape()
+    return "OK"
+}
+