SI-6526 Tail call elimination should descend deeper.

It wasn't traversing into Select nodes nor into the receiver of
a tail call.
Fix SI-6552, regression with self types.

In 6eb55d4b7a we put in a remedy for an old issue SI-4560 which
had accumulated a number of sketchy partial remedies which carried
no tests to illustrate their necessity. Looks like at least one of
those was doing something useful. Here's to reversion-reversion.

This reverts commit c8bdf199, which itself reverted cb4fd6582.
SI-6526 Additional test case.
Disabled generation of _1, _2, etc. methods.

This was part of the introduction of ProductN, which had
to go back into pandora's box because of issues with cycles
during typing.  These should have been reverted along
with it.
Merge pull request #1515 from paulp/issue/6552

Fix SI-6552, regression with self types.
Merge pull request #1507 from retronym/ticket/6526

SI-6526 Tail call elimination should descend deeper.
Merge pull request #1519 from paulp/no-product-n

Disabled generation of _1, _2, etc. methods.
New take on SI-6534, value classes.

Don't prohibit equals and hashCode in universal traits;
instead, always override them in value classes.
SI-6575 Plug inference leak of AbstractPartialFun

Usually this isn't needed, as partial functions can only be
defined with an expected type. But if that expected type is
and inherited method return type, the actual type of the partial
function literal is used, and the implementation detail of
`AbstractPartialFunction[A, B] with Serializable` leaks out.

After this change, the inferred types match those from
Scala 2.9.2.

ticket/6575 ~/code/scala scalac29 -Xprint:typer test/files/pos/t6575a.scala | grep def > 29.txt
ticket/6575 ~/code/scala squalac -Xprint:typer test/files/pos/t6575a.scala | grep def > 210.txt
ticket/6575 ~/code/scala diff -u 29.txt 210.txt
--- 29.txt	2012-10-28 13:51:07.000000000 +0100
+++ 210.txt	2012-10-28 13:51:20.000000000 +0100
@@ -1,7 +1,16 @@
     def foo: PartialFunction[Int,Int]
     def /*Y*/$init$(): Unit = {
-    absoverride def foo: PartialFunction[Int,Int] = ((x0$1: Int) => x0$1 match {
+    absoverride def foo: PartialFunction[Int,Int] = {
+        def <init>(): anonymous class $anonfun = {
+        final override def applyOrElse[A1 >: Nothing <: Int, B1 >: Int <: Any](x$1: A1, default: A1 => B1): B1 = (x$1: A1 @unchecked) match {
+        final def isDefinedAt(x$1: Int): Boolean = (x$1: Int @unchecked) match {
     def /*Z*/$init$(): Unit = {
-    absoverride def foo: PartialFunction[Int,Int] = ((x0$2: Int) => x0$2 match {
+    absoverride def foo: PartialFunction[Int,Int] = {
+        def <init>(): anonymous class $anonfun = {
+        final override def applyOrElse[A1 >: Nothing <: Int, B1 >: Int <: Any](x$1: A1, default: A1 => B1): B1 = (x$1: A1 @unchecked) match {
+        final def isDefinedAt(x$1: Int): Boolean = (x$1: Int @unchecked) match {
     def /*Comb*/$init$(): Unit = {
-    absoverride def foo: PartialFunction[Int,Int] = ((x0$3: Int) => x0$3 match {
+    absoverride def foo: PartialFunction[Int,Int] = {
+        def <init>(): anonymous class $anonfun = {
+        final override def applyOrElse[A1 >: Nothing <: Int, B1 >: Int <: Any](x$1: A1, default: A1 => B1): B1 = (x$1: A1 @unchecked) match {
+        final def isDefinedAt(x$1: Int): Boolean = (x$1: Int @unchecked) match {
Wider use and a new variant of typedPos.

It's safe to replace `localTyper.typed(atPos(pos)(tree))` with
`localTyper.typedPos(pos)(tree)` given that we're all in the
same cake and we'll get to the same `atPos`.
Fixes SI-5031 for separate compilation scenario.

When you have a conflicting member in package object and normal package that share the same namespace we remove the latter ClassSymbol from the scope. Now, this has an unpleasant consequence that companionClass/companionModule/companionSymbol no longer work correctly as they rely on finding the correspondent symbol using decls of the owner.
This fixes the problem of SI-5031 for separate compilation. Why the above change matters for finding foo.bar.Foo? Because when parsing the class we needed information about the static module (and we have the correct module symbol when completing the info). It's just that 043ce6d0565c9d5d960 relied on no longer valid assumptions. So we were getting NoSymbol and sym.exist was failing.

Obviously a more complete solution would be better if we didn't rely on the scope but that's too big to change for 2.10.0.
Use Typed rather than .setType

In response to pull request feedback.
SI-6581 fixed by inlining `Actor.self`.

This avoids the necessary type cast that was preventing leakage of internal migration classes.

Review by @phaller
Modification to SI-6534 patch.

Only exclude hashCode and equals from being overridden in
value classes, not other synthetics which may turn up such
as case class methods.
Fixes SI-6500 by making erasure more regular.

With the introduction of value classes, erasure uses specialErasure where a value class C with underlying type T is unboxed to an ErasedValueType. ErasedValue types are eliminated on phase later, in post-erasure. This was done everywhere, except in the parameter types of bridge methods. That was a mistale, because that way  bridge methods could not do the boxing/unboxing logic triggered by ErasedValueTypes.

Note: there is one remaining use of erasure (not specialErasure) in Erasure.scala. I put in a comment why that is OK.
Removing actors-migration from main repository so it can live on elsewhere.

* Removes actors-migration hooks from partest
* Removes actors-migration code
* removes actors-migration tests
* removes actors-migration distribution packaging.
SI-6556 no assert for surprising ctor result type

Previous fix to value classes uncovered some questionable cases in the backend where result types of constructor signatures are surprising. It's not a big deal because these types will be ignored afterwards anyway. But
the method uncovered some questionable situations which we should follow up on. However, breaking 2.9 code because of this is way too harsh. That's why the asserts were converted to warnings.

review by @paulp, @adriaanm
SI-6578 Harden against synthetics being added more than once.

Don't add synthetic methods if they already contain synthetic
methods from the set we're about to add.
Merge pull request #1530 from retronym/ticket/6575-2

SI-6575 Plug inference leak of AbstractPartialFunction
Merge pull request #1532 from hubertp/2.10.0-wip-issue/5031

Fixes SI-5031 for separate compilation scenario.