[stdlib] Add scala.language.2.13 to the scala 2 files (#23537)

This is a port of #23102 to the actual `main` branch.
---

In this PR, we add the import `scala.language.2.13` to each and every
file in the stdlib that originated from Scala 2.13.
The flag changes the behavior of certain part of the compiler to produce
code as if we were compiling with Scala 2.13's semantics.

Author: hamzaremmal

library/src/scala/AnyVal.scala.ignore

@@ -12,6 +12,8 @@
 
 package scala
 
+import scala.language.`2.13`
+
 /** `AnyVal` is the root class of all ''value types'', which describe values
  *  not implemented as objects in the underlying host system. Value classes
  *  are specified in Scala Language Specification, section 12.2.

library/src/scala/AnyValCompanion.scala

@@ -12,6 +12,8 @@
 
 package scala
 
+import scala.language.`2.13`
+
 /** A common supertype for companion classes of primitive types.
  *
  *  A common trait for /companion/ objects of primitive types comes handy

library/src/scala/App.scala

@@ -14,6 +14,8 @@ package scala
 
 import java.lang.System.{currentTimeMillis => currentTime}
 
+import scala.language.`2.13`
+
 import scala.annotation.nowarn
 import scala.collection.mutable.ListBuffer
 

library/src/scala/Array.scala

@@ -12,6 +12,8 @@
 
 package scala
 
+import scala.language.`2.13`
+
 //import scala.collection.generic._
 import scala.collection.{Factory, immutable, mutable}
 import mutable.ArrayBuilder

library/src/scala/Boolean.scala

@@ -16,6 +16,8 @@
 
 package scala
 
+import scala.language.`2.13`
+
 /** `Boolean` (equivalent to Java's `boolean` primitive type) is a
  *  subtype of [[scala.AnyVal]]. Instances of `Boolean` are not
  *  represented by an object in the underlying runtime system.

library/src/scala/Byte.scala

@@ -16,6 +16,8 @@
 
 package scala
 
+import scala.language.`2.13`
+
 /** `Byte`, a 8-bit signed integer (equivalent to Java's `byte` primitive type) is a
  *  subtype of [[scala.AnyVal]]. Instances of `Byte` are not
  *  represented by an object in the underlying runtime system.

library/src/scala/Char.scala

@@ -16,6 +16,8 @@
 
 package scala
 
+import scala.language.`2.13`
+
 /** `Char`, a 16-bit unsigned integer (equivalent to Java's `char` primitive type) is a
  *  subtype of [[scala.AnyVal]]. Instances of `Char` are not
  *  represented by an object in the underlying runtime system.

library/src/scala/Console.scala

@@ -12,6 +12,8 @@
 
 package scala
 
+import scala.language.`2.13`
+
 import java.io.{ BufferedReader, InputStream, InputStreamReader, OutputStream, PrintStream, Reader }
 import scala.io.AnsiColor
 import scala.util.DynamicVariable

library/src/scala/DelayedInit.scala

@@ -12,6 +12,8 @@
 
 package scala
 
+import scala.language.`2.13`
+
 /** Classes and objects (but note, not traits) inheriting the `DelayedInit`
  *  marker trait will have their initialization code rewritten as follows:
  *  `code` becomes `delayedInit(code)`.

library/src/scala/Double.scala

@@ -16,6 +16,8 @@
 
 package scala
 
+import scala.language.`2.13`
+
 /** `Double`, a 64-bit IEEE-754 floating point number (equivalent to Java's `double` primitive type) is a
  *  subtype of [[scala.AnyVal]]. Instances of `Double` are not
  *  represented by an object in the underlying runtime system.