SI-8829 Defaultly scala -feature -deprecation

Turn on `-feature -deprecation` in REPL if neither option
is selected.

```
$ ./build/pack/bin/scala
Welcome to Scala 2.12.0-20160707-105953-4e564ef (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_92).
Type in expressions for evaluation. Or try :help.

scala> @deprecated("","") def f = 42
f: Int

scala> f toDouble
<console>:13: warning: postfix operator toDouble should be enabled
by making the implicit value scala.language.postfixOps visible.
This can be achieved by adding the import clause 'import scala.language.postfixOps'
or by setting the compiler option -language:postfixOps.
See the Scaladoc for value scala.language.postfixOps for a discussion
why the feature should be explicitly enabled.
       f toDouble
         ^
<console>:13: warning: method f is deprecated:
       f toDouble
       ^
res1: Double = 42.0

scala> :quit
$ scala
Welcome to Scala 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_92).
Type in expressions for evaluation. Or try :help.

scala> @deprecated("","") def f = 42
f: Int

scala> f toDouble
warning: there was one deprecation warning; re-run with -deprecation for details
warning: there was one feature warning; re-run with -feature for details
res1: Double = 42.0

```

1 files changed, 5 insertions, 0 deletions

diff --git a/src/repl/scala/tools/nsc/MainGenericRunner.scala b/src/repl/scala/tools/nsc/MainGenericRunner.scala
index 747b684293..a09e797e07 100644
--- a/src/repl/scala/tools/nsc/MainGenericRunner.scala
+++ b/src/repl/scala/tools/nsc/MainGenericRunner.scala
@@ -71,6 +71,11 @@ class MainGenericRunner {
           Right(false)
         case _  =>
           // We start the repl when no arguments are given.
+          // If user is agnostic about both -feature and -deprecation, turn them on.
+          if (settings.deprecation.isDefault && settings.feature.isDefault) {
+            settings.deprecation.value = true
+            settings.feature.value = true
+          }
           Right(new interpreter.ILoop process settings)
       }