Add capture checking to scala.reflect

Just imports for now, no quotes support for capturing types yet

Author: natsukagami

library/src/scala/reflect/Enum.scala

@@ -1,5 +1,7 @@
 package scala.reflect
 
+import language.experimental.captureChecking
+
 /** A base trait of all Scala enum definitions */
 transparent trait Enum extends Any, Product, Serializable:
 

library/src/scala/reflect/Selectable.scala

@@ -1,5 +1,7 @@
 package scala.reflect
 
+import language.experimental.captureChecking
+
 /** A class that implements structural selections using Java reflection.
  *
  *  It can be used as a supertrait of a class or be made available

library/src/scala/reflect/TypeTest.scala

@@ -1,5 +1,7 @@
 package scala.reflect
 
+import language.experimental.captureChecking
+
 /** A `TypeTest[S, T]` contains the logic needed to know at runtime if a value of
  *  type `S` is an instance of `T`.
  *

library/src/scala/reflect/Typeable.scala

@@ -1,5 +1,7 @@
 package scala.reflect
 
+import language.experimental.captureChecking
+
 /** A shorhand for `TypeTest[Any, T]`. A `Typeable[T] contains the logic needed to
  *  know at runtime if a value can be downcasted to `T`.
  *