SI-2405 Confer implicit privileges to renamed imports.

Yin and yang would be pleased: A fix in two parts.

1. Use the name of the imported symbol, rather than the alias, in the generated `Select(qual, name)` tree.
2. Do the opposite in `isQualifyingImplicit`, which performs one part of the shadowing check.

But there is still work to do. The second part of the shadowing check, `nonImplicitSynonymInScope`,
fails to notice this case (irrespective of aliased imports).

  // Expecting shadowing #2. Alas, none is cast!
  object Test1 {
    object A { implicit val x: Int = 1 }
    import A.x
    def x: Int = 0
    implicitly[Int]
  }

I'm hitching the residual problem to SI-4270's wagon.

1 files changed, 8 insertions, 0 deletions

diff --git a/test/files/neg/t2405.check b/test/files/neg/t2405.check
new file mode 100644
index 0000000000..78360bcc21
--- /dev/null
+++ b/test/files/neg/t2405.check
@@ -0,0 +1,8 @@
+t2405.scala:6: warning: imported `y' is permanently hidden by definition of method y
+		import A.{x => y}
+                          ^
+t2405.scala:8: error: could not find implicit value for parameter e: Int
+		implicitly[Int]
+                          ^
+one warning found
+one error found