tests: Copy stdlib tests from Kotlin/JVM

This patch copies Kotlin/JVM stdlib tests (libraries/stdlib/test)
excepting ones with explicit java dependencies. It also transforms
the tests to use them as box-tests.

backend.native/tests/external/stdlib/text/StringTest/replaceDelimited.kt

@@ -0,0 +1,26 @@
+import kotlin.test.*
+
+
+
+fun box() {
+    val s = "/user/folder/file.extension"
+    // chars
+    assertEquals("/user/folder/file.doc", s.replaceAfter('.', "doc"))
+    assertEquals("/user/folder/another.doc", s.replaceAfterLast('/', "another.doc"))
+    assertEquals("new name.extension", s.replaceBefore('.', "new name"))
+    assertEquals("/new/path/file.extension", s.replaceBeforeLast('/', "/new/path"))
+
+    // strings
+    assertEquals("/user/folder/file.doc", s.replaceAfter(".", "doc"))
+    assertEquals("/user/folder/another.doc", s.replaceAfterLast("/", "another.doc"))
+    assertEquals("new name.extension", s.replaceBefore(".", "new name"))
+    assertEquals("/new/path/file.extension", s.replaceBeforeLast("/", "/new/path"))
+
+    // non-existing delimiter
+    assertEquals("/user/folder/file.extension", s.replaceAfter("=", "doc"))
+    assertEquals("/user/folder/file.extension", s.replaceAfterLast("=", "another.doc"))
+    assertEquals("/user/folder/file.extension", s.replaceBefore("=", "new name"))
+    assertEquals("/user/folder/file.extension", s.replaceBeforeLast("=", "/new/path"))
+    assertEquals("xxx", s.replaceBefore("=", "new name", "xxx"))
+    assertEquals("xxx", s.replaceBeforeLast("=", "/new/path", "xxx"))
+}