SI-8442 Ignore stub annotation symbols in `AnnotationInfo#matches`

And update the java `ClassFileParser` to create distinguished
`StubClassSymbol`s, rather that a regular `ClassSymbol`s, when
encountering a deficient classpath. This brings it into line
with `Unpickler`, which has done as much since a55788e275f.

This stops the enclosed test case from crashing when determining
if the absent symbol, `A_1`, is a subclass of `@deprecated`.

This is ostensibly fixes a regression, although it only worked in
`2.10.[0-3]` by a fluke: the class file parser's promiscious
exception handling caught and recovered from the NPE introduced
in SI-7439!

	% javac -d /tmp test/files/run/t8442/{A,B}_1.java &&  qbin/scalac -classpath /tmp -d /tmp test/files/run/t8442/C_2.scala && (rm /tmp/A_1.class; true) && scalac-hash v2.10.0 -classpath /tmp -d /tmp test/files/run/t8442/C_2.scala
	warning: Class A_1 not found - continuing with a stub.
	warning: Caught: java.lang.NullPointerException while parsing annotations in /tmp/B_1.class
	two warnings found

1 files changed, 29 insertions, 0 deletions

diff --git a/test/files/run/t8442/Test.scala b/test/files/run/t8442/Test.scala
new file mode 100644
index 0000000000..ff6da4e206
--- /dev/null
+++ b/test/files/run/t8442/Test.scala
@@ -0,0 +1,29 @@
+import scala.tools.partest._
+import java.io.File
+
+object Test extends StoreReporterDirectTest {
+  def code = ???
+
+  def compileCode(code: String) = {
+    val classpath = List(sys.props("partest.lib"), testOutput.path) mkString sys.props("path.separator")
+    compileString(newCompiler("-cp", classpath, "-d", testOutput.path))(code)
+  }
+
+  def app = """
+    class C_2 {
+      def foo(b: B_1) {
+        b.get()
+      }
+    }
+  """
+
+  def show(): Unit = {
+    val tClass = new File(testOutput.path, "A_1.class")
+    assert(tClass.exists)
+    assert(tClass.delete())
+
+    // Expecting stub symbol warning, but no stack trace!
+    compileCode(app)
+    println(filteredInfos.mkString("\n"))
+  }
+}