SI-9350 Command option -Xreporter

Add a setting to take a custom Reporter.

Example of reporter that discounts deprecations for purposes of
(not) failing the build:

```
import scala.tools.nsc.Settings
import scala.tools.nsc.reporters.ConsoleReporter

import scala.reflect.internal.util._

class MyReporter(ss: Settings) extends ConsoleReporter(ss) {
  var deprecationCount = 0
  override def warning(pos: Position, msg: String): Unit = {
    if (msg contains "is deprecated") deprecationCount += 1
    super.warning(pos, msg)
  }
  override def hasWarnings: Boolean = count(WARNING) - deprecationCount > 0
  override def reset() = { deprecationCount = 0 ; super.reset() }
}
```

Invoked as:

```
$ scalac -toolcp . -Xreporter myrep.MyReporter -Xfatal-warnings -deprecation test.scala
test.scala:8: warning: class C in package tester is deprecated: Don't use me
  Console println s"${new C}"
                          ^
one warning found
```

where the reporter class is in the current directory, placed on the tool class path.

Also flush on early-reported errors.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/nsc/reporters/ConsoleReporter.scala b/src/compiler/scala/tools/nsc/reporters/ConsoleReporter.scala
index 5bf611a7b0..4bf92fd1fb 100644
--- a/src/compiler/scala/tools/nsc/reporters/ConsoleReporter.scala
+++ b/src/compiler/scala/tools/nsc/reporters/ConsoleReporter.scala
@@ -11,8 +11,7 @@ import java.io.{ BufferedReader, IOException, PrintWriter }
 import scala.reflect.internal.util._
 import StringOps._
 
-/**
- * This class implements a Reporter that displays messages on a text console.
+/** This class implements a Reporter that displays messages on a text console.
  */
 class ConsoleReporter(val settings: Settings, reader: BufferedReader, writer: PrintWriter) extends AbstractReporter {
   def this(settings: Settings) = this(settings, Console.in, new PrintWriter(Console.err, true))
@@ -85,5 +84,7 @@ class ConsoleReporter(val settings: Settings, reader: BufferedReader, writer: Pr
     }
   }
 
-  override def flush() { writer.flush() }
+  override def flush() = writer.flush()
+
+  override def finish() = printSummary()
 }