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, 5 insertions, 2 deletions

diff --git a/test/files/run/stringbuilder.scala b/test/files/run/stringbuilder.scala
index ef85fc02a6..a88ea38b92 100644
--- a/test/files/run/stringbuilder.scala
+++ b/test/files/run/stringbuilder.scala
@@ -1,3 +1,6 @@
+
+import scala.language.reflectiveCalls
+
 object Test extends App {
   val str = "ABCDEFGHIJKLMABCDEFGHIJKLM"
   val surrogateStr = "an old Turkic letter: \uD803\uDC22"
@@ -33,8 +36,8 @@ object Test extends App {
   sameAnswers(_.lastIndexOf("KLM", 22))
   
   // testing that the "reverse" implementation avoids reversing surrogate pairs
-  val jsb = new JavaStringBuilder(surrogateStr) reverse
-  val ssb = new ScalaStringBuilder(surrogateStr) reverseContents ;
+  val jsb = new JavaStringBuilder(surrogateStr).reverse
+  val ssb = new ScalaStringBuilder(surrogateStr).reverseContents
   
   assert(jsb.toString == ssb.toString)
 }