SI-8711 ScalaVersion.unparse doesn't produce valid versions

There is no dot between `major.minor.rev` and `-build` in a scala
version, yet that's what unparse returns for

```
// was "2.11.3.-SNAPSHOT"
ScalaVersion("2.11.3-SNAPSHOT").unparse
```

1 files changed, 18 insertions, 0 deletions

diff --git a/test/junit/scala/tools/nsc/settings/ScalaVersionTest.scala b/test/junit/scala/tools/nsc/settings/ScalaVersionTest.scala
new file mode 100644
index 0000000000..77a2da828e
--- /dev/null
+++ b/test/junit/scala/tools/nsc/settings/ScalaVersionTest.scala
@@ -0,0 +1,18 @@
+package scala.tools.nsc
+package settings
+
+import org.junit.Assert._
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import scala.tools.testing.AssertUtil.assertThrows
+
+@RunWith(classOf[JUnit4])
+class ScalaVersionTest {
+  // SI-8711
+  @Test def versionUnparse() {
+    val v = "2.11.3"
+
+    assertEquals(ScalaVersion(v).unparse, v)
+  }
+}