SI-7499 Additional test case for SI-7319

From a duplicate ticket.
SI-3425 erasure crash with refinement members.

Checking that a refinement class symbol does not override
any symbols does mean it will have to be invoke reflectively;
but the converse is not true. It can override other symbols
and still have to be called reflectively, because the
overridden symbols may also be defined in refinement classes.

  scala> class Foo { type R1 <: { def x: Any } ; type R2 <: R1 { def x: Int }  }
  defined class Foo

  scala> typeOf[Foo].member(TypeName("R2")).info.member("x": TermName).overrideChain
  res1: List[$r.intp.global.Symbol] = List(method x, method x)

  scala> res1 filterNot (_.owner.isRefinementClass)
  res2: List[$r.intp.global.Symbol] = List()

And checking that "owner.info decl name == this" only works if
name is not overloaded.

So the logic is all in "isOnlyRefinementMember" now, and
let's hope that suffices for a while.
Added another test.

Probably overshot the mark a little.
Merge pull request #2574 from paulp/issue/3425

SI-3425 erasure crash with refinement members.
Merge pull request #2573 from retronym/ticket/7499

SI-7499 Additional test case for SI-7319
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.