report error when using null literal as default expression of non-null

report error when using null literal as default expression of non-null

2008-04-14  Juerg Billeter  <j@bitron.ch>

	* vala/valasemanticanalyzer.vala: report error when using null
	  literal as default expression of non-null parameter,
	  fixes bug 528021

	* gee/readonlycollection.vala, gee/readonlylist.vala,
	  gee/readonlymap.vala, gee/readonlyset.vala, vala/valascope.vala,
	  ccode/valaccodeforstatement.vala, ccode/valaccodewhilestatement.vala,
	  vapigen/valavapicheck.vala, vapi/glib-2.0.vapi: fix revealed bugs

svn path=/trunk/; revision=1226