SI-3368 CDATA gets a Node

XML Parser uses `scala.xml.PCData`.

A compiler flag `-Yxml:coalescing`, analogous to
`DocumentBuilderFactory.setCoalescing`, turns `PCData`
nodes into `Text` nodes and coalesces sibling text nodes.

This change also fixes parse errors such as rejecting a
sequence of CDATA sections.

A sequence of "top level" nodes are not coalesced.

```
scala> <a><b/>start<![CDATA[hi & bye]]><c/>world<d/>stuff<![CDATA[red & black]]></a>
res0: scala.xml.Elem = <a><b/>start<![CDATA[hi & bye]]><c/>world<d/>stuff<![CDATA[red & black]]></a>

scala> :replay -Yxml:coalescing
Replaying: <a><b/>start<![CDATA[hi & bye]]><c/>world<d/>stuff<![CDATA[red & black]]></a>
res0: scala.xml.Elem = <a><b/>starthi &amp; bye<c/>world<d/>stuffred &amp; black</a>
```

1 files changed, 21 insertions, 0 deletions

diff --git a/src/partest-extras/scala/tools/partest/ParserTest.scala b/src/partest-extras/scala/tools/partest/ParserTest.scala
new file mode 100644
index 0000000000..e4c92e3dc3
--- /dev/null
+++ b/src/partest-extras/scala/tools/partest/ParserTest.scala
@@ -0,0 +1,21 @@
+/* NSC -- new Scala compiler
+ * Copyright 2005-2014 LAMP/EPFL
+ */
+
+package scala.tools.partest
+
+/** A class for testing parser output.
+ *  Just supply the `code` and update the check file.
+ */
+abstract class ParserTest extends DirectTest {
+
+  override def extraSettings: String = "-usejavacp -Ystop-after:parser -Xprint:parser"
+
+  override def show(): Unit = {
+    // redirect err to out, for logging
+    val prevErr = System.err
+    System.setErr(System.out)
+    compile()
+    System.setErr(prevErr)
+  }
+}