Selective dealiasing when printing errors.

*** Important note for busy commit log skimmers ***

Symbol method "fullName" has been trying to serve the dual role of "how
to print a symbol" and "how to find a class file." It cannot serve both
these roles simultaneously, primarily because of package objects but
other little things as well. Since in the majority of situations we want
the one which corresponds to the idealized scala world, not the grubby
bytecode, I went with that for fullName. When you require the path to a
class (e.g. you are calling Class.forName) you should use javaClassName.

  package foo { package object bar { class Bippy } }

If sym is Bippy's symbol, then

       sym.fullName == foo.bar.Bippy
  sym.javaClassName == foo.bar.package.Bippy

*** End important note ***

There are many situations where we (until now) forewent revealing
everything we knew about a type mismatch. For instance, this isn't very
helpful of scalac (at least in those more common cases where you didn't
define type X on the previous repl line.)

  scala> type X = Int
  defined type alias X

  scala> def f(x: X): Byte = x
  <console>:8: error: type mismatch;
   found   : X
   required: Byte
         def f(x: X): Byte = x
                             ^
Now it says:

   found   : X
      (which expands to)  Int
   required: Byte
         def f(x: X): Byte = x
                             ^

In addition I rearchitected a number of methods involving:

 - finding a symbol's owner
 - calculating a symbol's name
 - determining whether to print a prefix

No review.

Author: paulp

test/files/jvm/interpreter.check

@@ -35,8 +35,9 @@ four: anotherint = 4
 
 scala> val bogus: anotherint = "hello"
 <console>:8: error: type mismatch;
- found   : java.lang.String("hello")
+ found   : String("hello")
  required: anotherint
+    (which expands to)  Int
        val bogus: anotherint = "hello"
                                ^
 
@@ -73,7 +74,7 @@ fish: S = fish
 scala> // Test that arrays pretty print nicely.
 
 scala> val arr = Array("What's", "up", "doc?") 
-arr: Array[java.lang.String] = Array(What's, up, doc?)
+arr: Array[String] = Array(What's, up, doc?)
 
 scala> // Test that arrays pretty print nicely, even when we give them type Any
 
@@ -263,7 +264,7 @@ scala> xs filter (_ == 2)
 res4: Array[_] = Array(2)
 
 scala> xs map (_ => "abc")
-res5: Array[java.lang.String] = Array(abc, abc)
+res5: Array[String] = Array(abc, abc)
 
 scala> xs map (x => x)
 res6: scala.collection.mutable.ArraySeq[_] = ArraySeq(1, 2)
@@ -322,7 +323,7 @@ scala> """
 hello
 there
 """
-res9: java.lang.String = 
+res9: String = 
 "
 hello
 there
@@ -368,7 +369,7 @@ scala>
 scala> 
 plusOne: (x: Int)Int
 res0: Int = 6
-res1: java.lang.String = after reset
+res1: String = after reset
 <console>:8: error: not found: value plusOne
               plusOne(5) // should be undefined now
               ^