Replace NamespaceReference by UsingDirective and UnresolvedSymbol, fixes

Replace NamespaceReference by UsingDirective and UnresolvedSymbol, fixes

2008-09-26  Jürg Billeter  <j@bitron.ch>

	* vala/Makefile.am:
	* vala/valacodevisitor.vala:
	* vala/valagenieparser.vala:
	* vala/valaparser.vala:
	* vala/valasemanticanalyzer.vala:
	* vala/valasourcefile.vala:
	* vala/valasymbolresolver.vala:
	* vala/valaunresolvedsymbol.vala:
	* vala/valausingdirective.vala:
	* compiler/valacompiler.vala:

	Replace NamespaceReference by UsingDirective and UnresolvedSymbol,
	fixes bug 537510

	* tests/namespaces.vala:

	Test using directive with nested namespaces

svn path=/trunk/; revision=1783