SI-7003 Partest redirects stderr to log file

Some scalac output is on stderr, and it's useful to see that
in the log file, especially for debugging.

Adds a line filter for logs, specified as "filter: pattern"
in the test source.

Backslashes are made forward only when detected as paths.

Test alignments:

Deprecations which do not pertain to the system under test
are corrected in the obvious way.

When testing deprecated API, suppress warnings by deprecating
the Test object.

Check files are updated with useful true warnings, instead of
running under -nowarn.

Language feature imports as required, instead of running under -language.

Language feature not required, such as casual use of postfix.

Heed useful warning.

Ignore broken warnings. (Rarely, -nowarn.)

Inliner warnings pop up under -optimise only, so for now, just
filter them out where they occur.

Debug output from the test required an update.

1 files changed, 23 insertions, 22 deletions

diff --git a/test/files/run/concurrent-stream.scala b/test/files/run/concurrent-stream.scala
index 42c695964e..9d5ba0428e 100644
--- a/test/files/run/concurrent-stream.scala
+++ b/test/files/run/concurrent-stream.scala
@@ -1,32 +1,33 @@
 // test concurrent calls to Stream.tail
+@deprecated("Suppress warnings", since="2.11")
 object Test  {
 
-def slowRange(from: Int, until: Int, cons: (Int, => Stream[Int]) => Stream[Int]): Stream[Int] = {
-  var current = from
-  def next: Stream[Int] = {
-    Thread.sleep(100)
-    if (current >= until) Stream.empty
-    else {
-      val stream = cons(current, next)
-      current += 1
-      stream
+  def slowRange(from: Int, until: Int, cons: (Int, => Stream[Int]) => Stream[Int]): Stream[Int] = {
+    var current = from
+    def next: Stream[Int] = {
+      Thread.sleep(100)
+      if (current >= until) Stream.empty
+      else {
+        val stream = cons(current, next)
+        current += 1
+        stream
+      }
     }
+    next
   }
-  next
-}
 
-def testCons(cons: (Int, => Stream[Int]) => Stream[Int]): Unit = {
-  import scala.actors.Actor._
+  def testCons(cons: (Int, => Stream[Int]) => Stream[Int]): Unit = {
+    import scala.actors.Actor._
 
-  val stream = slowRange(0, 10, cons)
-  val main = self
-  actor { main ! stream.toList }
-  actor { main ! stream.toList }
-  val eval0 = receive { case list: List[Int] => list }
-  val eval1 = receive { case list: List[Int] => list }
-  println("Evaluation 0: " + eval0)
-  println("Evaluation 1: " + eval1)
-}
+    val stream = slowRange(0, 10, cons)
+    val main = self
+    actor { main ! stream.toList }
+    actor { main ! stream.toList }
+    val eval0 = receive { case list: List[Int @unchecked] => list }
+    val eval1 = receive { case list: List[Int @unchecked] => list }
+    println("Evaluation 0: " + eval0)
+    println("Evaluation 1: " + eval1)
+  }
 
   def main(args: Array[String]) {
     println("Testing standard cons.")