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, 28 insertions, 0 deletions

diff --git a/test/files/jvm/t7006.check b/test/files/jvm/t7006.check
new file mode 100644
index 0000000000..7c99eba30c
--- /dev/null
+++ b/test/files/jvm/t7006.check
@@ -0,0 +1,28 @@
+[running phase parser on Foo_1.scala]
+[running phase namer on Foo_1.scala]
+[running phase packageobjects on Foo_1.scala]
+[running phase typer on Foo_1.scala]
+[running phase patmat on Foo_1.scala]
+[running phase superaccessors on Foo_1.scala]
+[running phase extmethods on Foo_1.scala]
+[running phase pickler on Foo_1.scala]
+[running phase refchecks on Foo_1.scala]
+[running phase uncurry on Foo_1.scala]
+[running phase tailcalls on Foo_1.scala]
+[running phase specialize on Foo_1.scala]
+[running phase explicitouter on Foo_1.scala]
+[running phase erasure on Foo_1.scala]
+[running phase posterasure on Foo_1.scala]
+[running phase lazyvals on Foo_1.scala]
+[running phase lambdalift on Foo_1.scala]
+[running phase constructors on Foo_1.scala]
+[running phase flatten on Foo_1.scala]
+[running phase mixin on Foo_1.scala]
+[running phase cleanup on Foo_1.scala]
+[running phase icode on Foo_1.scala]
+[running phase inliner on Foo_1.scala]
+[running phase inlinehandlers on Foo_1.scala]
+[running phase closelim on Foo_1.scala]
+[running phase constopt on Foo_1.scala]
+[running phase dce on Foo_1.scala]
+[running phase jvm on icode]