XML ConstructingParser too aggressive trimming whitespace around character references

[mbeckerle]

This issue migrated from https://issues.scala-lang.org/browse/SI-3527.

Original description of the issue:

when preserveWS = false. example:

Welcome to Scala version 2.8.0.RC3 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_20).

scala> xml.parsing.ConstructingParser.fromSource(io.Source.fromString("<x>a &amp; b</x>"), preserveWS = false).document.text
res0: String = a&b

note that spaces on either side of the escaped ampersand have been lost.

I can't see why you would ever want this behavior. and I'm not an XML laywer, but section 4.4 of the XML 1.0 spec suggests that the character encoded by a character reference should be "retrieved and processed, in place of the reference itself, as though it were part of the document at the location the reference was recognized"

perhaps vaguely related: #73