Move sharable/unshared annotations to dotty-library

Previously they were in dotty-compiler, which means that running
`-Ycheck:reentrant` on a non-bootstrapped compiler would try to load
symbols from the non-bootstrapped compiler itself.

Author: smarter

compiler/src/dotty/tools/dotc/Bench.scala

@@ -4,6 +4,8 @@ package dotc
 import core.Contexts.Context
 import reporting.Reporter
 
+import scala.annotation.internal.sharable
+
 /** A main class for running compiler benchmarks. Can instantiate a given
  *  number of compilers and run each (sequentially) a given number of times
  *  on the same sources.

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -13,6 +13,8 @@ import collection.mutable.ListBuffer
 import reporting.diagnostic.messages._
 import reporting.trace
 
+import scala.annotation.internal.sharable
+
 object desugar {
   import untpd._
   import DesugarEnums._

compiler/src/dotty/tools/dotc/ast/DesugarEnums.scala

@@ -10,6 +10,8 @@ import collection.mutable.ListBuffer
 import util.Property
 import typer.ErrorReporting._
 
+import scala.annotation.internal.sharable
+
 /** Helper methods to desugar enums */
 object DesugarEnums {
   import untpd._

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -14,6 +14,7 @@ import parsing.Tokens.Token
 import printing.Printer
 import util.{Stats, Attachment, Property, DotClass}
 import config.Config
+import annotation.internal.sharable
 import annotation.unchecked.uncheckedVariance
 import language.implicitConversions
 

compiler/src/dotty/tools/dotc/ast/untpd.scala

@@ -11,6 +11,8 @@ import language.higherKinds
 import collection.mutable.ListBuffer
 import reflect.ClassTag
 
+import scala.annotation.internal.sharable
+
 object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
 
   // ----- Tree cases that exist in untyped form only ------------------

compiler/src/dotty/tools/dotc/config/CommandLineParser.scala

@@ -2,7 +2,7 @@ package dotty.tools.dotc
 package config
 
 import scala.annotation.tailrec
-import dotty.tools.sharable
+import scala.annotation.internal.sharable
 
 /** A simple (overly so) command line parser.
  *  !!! This needs a thorough test suite to make sure quoting is

compiler/src/dotty/tools/dotc/config/Properties.scala

@@ -2,6 +2,8 @@ package dotty.tools
 package dotc
 package config
 
+import scala.annotation.internal.sharable
+
 import java.io.{ IOException, PrintWriter }
 import java.util.jar.Attributes.{ Name => AttributeName }
 

compiler/src/dotty/tools/dotc/config/ScalaVersion.scala

@@ -3,6 +3,7 @@
 package dotty.tools
 package dotc.config
 
+import scala.annotation.internal.sharable
 import scala.util.{Try, Success, Failure}
 
 /**

compiler/src/dotty/tools/dotc/core/Contexts.scala

@@ -29,6 +29,8 @@ import collection.immutable.BitSet
 import printing._
 import config.{JavaPlatform, Platform, ScalaSettings, Settings}
 
+import scala.annotation.internal.sharable
+
 import language.implicitConversions
 import DenotTransformers.DenotTransformer
 import dotty.tools.dotc.profile.Profiler

compiler/src/dotty/tools/dotc/core/NameKinds.scala

@@ -11,6 +11,8 @@ import Decorators._
 import Contexts.Context
 import collection.mutable
 
+import scala.annotation.internal.sharable
+
 /** Defines possible kinds of NameInfo of a derived name */
 object NameKinds {