Add new config for PrettyPrinter to minimize empty tags #90

	* src/main/scala/scala/xml/PrettyPrinter.scala (PrettyPrinter):
	New parameter minimizeEmpty.
	(PrettyPrinter.traverse): Pass config for minimizeTags to
	Utility.serialize().

	* src/test/scala/scala/xml/UtilityTest.scala (issue90): New test.

	* src/test/scala/scala/xml/XMLTest.scala (issue90): New test.

jvm/src/test/scala/scala/xml/XMLTest.scala

@@ -555,4 +555,11 @@ class XMLTestJVM {
     assertEquals("<node/>", pp.format(x.copy(minimizeEmpty = true)))
   }
 
+  @UnitTest
+  def issue90: Unit = {
+    val pp = new xml.PrettyPrinter(80, 2, minimizeEmpty = true)
+    val x = <node><leaf></leaf></node>
+    assertEquals("<node>\n  <leaf/>\n</node>", pp.format(x))
+  }
+
 }

shared/src/main/scala/scala/xml/PrettyPrinter.scala

@@ -23,8 +23,9 @@ import Utility.sbToString
  *  @param width the width to fit the output into
  *  @param step  indentation
  */
-class PrettyPrinter(width: Int, step: Int) {
+class PrettyPrinter(width: Int, step: Int, minimizeEmpty: Boolean = false) {
 
+  val minimizeMode = if (minimizeEmpty) MinimizeMode.Always else MinimizeMode.Default
   class BrokenException() extends java.lang.Exception
 
   class Item
@@ -150,7 +151,7 @@ class PrettyPrinter(width: Int, step: Int) {
     case _ =>
       val test = {
         val sb = new StringBuilder()
-        Utility.serialize(node, pscope, sb, stripComments = false)
+        Utility.serialize(node, pscope, sb, stripComments = false, minimizeTags = minimizeMode)
         if (doPreserve(node)) sb.toString
         else TextBuffer.fromString(sb.toString).toText(0).data
       }

shared/src/test/scala/scala/xml/UtilityTest.scala

@@ -51,4 +51,10 @@ class UtilityTest {
     </hi>.hashCode // Bug #777
   }
 
+  @Test
+  def issue90: Unit = {
+    val x = <node><leaf></leaf></node>
+    assertEquals("<node><leaf/></node>", Utility.serialize(x, minimizeTags = MinimizeMode.Always).toString)
+  }
+
 }