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, 10 insertions, 4 deletions

diff --git a/test/files/run/xml-loop-bug.scala b/test/files/run/xml-loop-bug.scala
index 67637674b2..dc155dbb02 100644
--- a/test/files/run/xml-loop-bug.scala
+++ b/test/files/run/xml-loop-bug.scala
@@ -1,8 +1,14 @@
+import java.io.{ Console => _, _ }
+import scala.io._
+import scala.xml.parsing._
 object Test {
   def main(args: Array[String]): Unit = {
-    val sink = new java.io.PrintStream(new java.io.ByteArrayOutputStream())
-    Console setOut sink
-    Console setErr sink
-    scala.xml.parsing.ConstructingParser.fromSource(scala.io.Source.fromString("<!DOCTYPE xmeml SYSTEM> <xmeml> <sequence> </sequence> </xmeml> "), true).document.docElem 
+    val xml = "<!DOCTYPE xmeml SYSTEM> <xmeml> <sequence> </sequence> </xmeml> "
+    val sink = new PrintStream(new ByteArrayOutputStream())
+    (Console withOut sink) {
+      (Console withErr sink) {
+        ConstructingParser.fromSource((Source fromString xml), true).document.docElem 
+      }
+    }
   }
 }