Added +: and :+ extractors to mirror append/prepend.

* +: does head/tail decomposition on any Seq
* :+ does init/last decomposition on any Seq
* Both preserve specific Seq types.

Review by @odersky
Library for ansi color management.

Having now experienced the unbelievable difference it makes to
have one's voluminous debugging output effectively color-coded,
I had to librarize the ansi codes in order to use them.  This
could all go in the standard library, or as soon as I can easily
make use of compiler dependencies, a separate library altogether.
For now it hides away in scala.tools.util.color.
Merge remote-tracking branches 'axel22/feature/checkinit-transient' and 'jsuereth/mirrored-seq-extractors' into develop
Merge branch 'mar17-colorize'
Fixed versioning scheme when running on a tag.

git describe is useless in that situation, afaict.
First cut at a release notes tool to help generate them.
SI-5189: refined GADT soundness fix

extrapolate GADT skolems: only complicate types when needed
make sure we only deskolemize GADT skolems after typedCase
Separating Scala Actors from the Scala Library.

Scala actors are now in scala-actors.jar. Changes that were done are:
 - Fixed partest to include actors library for various test usages
 - Created the entry for the new jar in build.xml
 - Added maven entries for scala actors

Review by: @jsuereth
Tree adjustments.

I noticed that if we gave Ident a "qualifier" method which is
always EmptyTree, a whole bunch of code could be simplified.

A transparent subclass of Apply which preserves the source
level "new" a little longer than never.

Since productPrefix is tied up in reification - and oh I
detest this "String"-based programming, we shouldn't have to
wait until everyone learns this independently to change it -
I added "printingPrefix" to Tree, which defaults to
productPrefix but can be changed without breaking reify.
Overhaul of NodePrinters.

Drawing on the previous, a half-decade overdue overhaul of
NodePrinters.  Now with colors if you like colors.

% scalac -Xprint:all -Yshow-trees -Dscala.colors a.scala

Am heading toward general purpose color configuration.
Chill out repl ctrl-char filter.

So colors can come through unscathed.
Merge remote-tracking branch 'adriaanm/ticket/5189' into develop
Merge remote-tracking branch 'vjovanov/actors-move' into develop
Adapted indentation in scaladoc code blocks

and fixed a pesky crash in the syntax highlighting caused by invalid
chars (0x0E) in MarkupParser.scala.
Adapted usecases to full signature display
Finally did something about broken irrefutability.

The parser has always been confused about tuple patterns in
for comprehensions.  It thinks it can fail to recognize an
irrefutable pattern and have it removed in refchecks, but it
is sadly mistaken, because the unnecessary filter has a tendency
to fail the compile in typer.

Look more intently for irrefutable patterns and don't insert
the unnecessary filter.  Closes SI-5589, SI-1336.
Discovered filter was still being generated.

Rather than withFilter, for a subset of for comprehension structures.
Not sure if this was somewhat by design - only seems possible because
refchecks was only looking for nme.filter, not nme.withFilter, so
perhaps this was intended as some secret irrefutability backchannel?
Really have to document that sort of thing if it's intentional.  I
assumed it wasn't and unified everything.
Spiced up the irrefutability tests a bit.
Test cases closes SI-4574.

Looks like I got that irrefutability bug too.
Yet another attempt to make the version a  good one

This fixes the git commit drift issue and gives us enough granularity
to make releases at any time that are cronologically increasing.