Reflect the fact that FixedPoint is experimental. (freechipsproject#89)

* Reflect the fact that FixedPoint is experimental.

* Add import of chisel3.experimental for FixedPoint.

Author: ucbjrl

src/main/scala/chisel3/iotesters/VerilatorBackend.scala

@@ -8,7 +8,8 @@ import java.io.{File, FileWriter, IOException, PrintStream, Writer}
 import java.nio.file.{FileAlreadyExistsException, Files, Paths}
 import java.nio.file.StandardCopyOption.REPLACE_EXISTING
 
-import chisel3.{SInt, FixedPoint}
+import chisel3.SInt
+import chisel3.experimental.FixedPoint
 
 /**
   * Copies the necessary header files used for verilator compilation to the specified destination folder

src/test/scala/examples/Adder.scala

@@ -3,6 +3,7 @@
 package examples
 
 import chisel3._
+import chisel3.experimental.FixedPoint
 import chisel3.iotesters.{ChiselFlatSpec, Exerciser, PeekPokeTester, SteppedHWIOTester}
 import org.scalatest.{FreeSpec, Matchers}