synchronized with git master (g008a781 aka 4107)

synchronized with git master (g0947d08 aka 4094)

synchronized with g210cdce (master)

Fix for octal test.

At the last minute I made -Xfuture leading-0 an error and
failed to update the checkfile.

Fixed -Xfuture 5.ds, deprecated 0-octal.

I messed up my trip to the future the first time around; now in
the future 5.f is not an error but an attempt to call method "f"
on 5 like nature intended. (Thank you simon for catching this.)
And deprecated leading 0 for octal. Closes SI-5205.

Fix for build.xml classpaths.

Found the cause of plugin build failures which have long haunted me at
inopportune times. It's all built against locker instead of quick.
Kind of a buzzkill to be fixing this during the "Ant End Times" but
better now than never.

Added the check against UnitClass in freeLocalsTraverser.
Closes SI-5245. Review by odersky.

Attempt to fix #5230. Review by burmako.

-Yreify-copypaste: the copy/pasteable mode for reification

When experimenting with macros, I've found out that it's helpful
to use the reifier to find out what Scala idioms map to what Tree shapes.
However, stuff emitted by -Yreify-debug is too verbose, that's why I decided
to put up a human-readable dumper.

To use the dumps, you need to first import the following things:
import scala.reflect.api._
import scala.reflect.mirror._
import scala.reflect.api.Modifier._
import scala.reflect.internal.Flags._

The stuff is really experimental, e.g. the tension between flags and modifiers
needs to be thought out and addressed. Review by odersky.

Reflection toolboxes now respect settings that are provided to them.

Before the fix CompilerCommand lacked the (args, settings, errorFn) ctor.
I added it and provided means to augment passed settings with custom errorFn.

Closes SI-5239. Review by odersky.