More liberal matching in REPL autocompletion

For the SHIFT-impaired: you can just write everything in lowercase,
(whisper-case?) and we'll try to DWYM.

We treat capital letters that you *do* enter as significant, they
can't match a lower case letter in an identifier.

Modelled after IntellIJ's completion.

I still don't fall into this mode if you enter an exact prefix of
a candidate, but we might consider changing that.

```
scala> classOf[String].typ<TAB>
   getAnnotationsByType   getComponentType   getDeclaredAnnotationsByType   getTypeName   getTypeParameters

scala> classOf[String].typN<TAB>
scala> classOf[String].getTypeName
res3: String = java.lang.String

scala> def foo(s: str<TAB>
scala> def foo(s: String
String   StringBuffer   StringBuilder   StringCanBuildFrom   StringContext   StringFormat   StringIndexOutOfBoundsException

scala> def foo(s: string<TAB>
scala> def foo(s: String
String   StringBuffer   StringBuilder   StringCanBuildFrom   StringContext   StringFormat   StringIndexOutOfBoundsException
```

1 files changed, 9 insertions, 0 deletions

diff --git a/test/junit/scala/tools/nsc/interpreter/CompletionTest.scala b/test/junit/scala/tools/nsc/interpreter/CompletionTest.scala
index a55a3c66c0..534d5ddc3a 100644
--- a/test/junit/scala/tools/nsc/interpreter/CompletionTest.scala
+++ b/test/junit/scala/tools/nsc/interpreter/CompletionTest.scala
@@ -63,6 +63,15 @@ class CompletionTest {
   }
 
   @Test
+  def lenientCamelCompletions(): Unit = {
+    val intp = newIMain()
+    val completer = new PresentationCompilerCompleter(intp)
+    checkExact(completer, "object O { def theCatSatOnTheMat = 1 }; import O._; tcso")("theCatSatOnTheMat")
+    checkExact(completer, "object O { def theCatSatOnTheMat = 1 }; import O._; sotm")("theCatSatOnTheMat")
+    checkExact(completer, "object O { def theCatSatOnTheMat = 1 }; import O._; TCSOTM")()
+  }
+
+  @Test
   def previousLineCompletions(): Unit = {
     val intp = newIMain()
     intp.interpret("class C { val x_y_z = 42 }")