PathResolver constructor: restore source compat and bincompat

small followup to scala#7712. the community build found that a couple of
projects (mima, twotails) were using the old constructor. since
it's easy to do, let's keep both source compat (with the default
arguent) and bincompat (with the extra constructor, which we can
toss for 2.13)

src/compiler/scala/tools/util/PathResolver.scala

@@ -206,7 +206,11 @@ object PathResolver {
     }
 }
 
-final class PathResolver(settings: Settings, closeableRegistry: CloseableRegistry) {
+final class PathResolver(settings: Settings, closeableRegistry: CloseableRegistry = new CloseableRegistry) {
+
+  @deprecated("for bincompat in 2.12.x series", "2.12.9")  // TODO remove from 2.13.x
+  def this(settings: Settings) = this(settings, new CloseableRegistry)
+
   private val classPathFactory = new ClassPathFactory(settings, closeableRegistry)
 
   import PathResolver.{ AsLines, Defaults, ppcp }