C++: Fix ::A name handling in findMatchingDeclaration.

Change-Id: Id158be80c42056c145c2b787d4f569e2c0a0b66e
Reviewed-on: http://codereview.qt.nokia.com/2932
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Christian Kamm <christian.d.kamm@nokia.com>

src/libs/cplusplus/CppDocument.cpp

@@ -1115,6 +1115,8 @@ void CPlusPlus::findMatchingDeclaration(const LookupContext &context,
     if (qName) {
         if (qName->base())
             binding = context.lookupType(qName->base(), enclosingScope);
+        else
+            binding = context.globalNamespace();
         functionName = qName->name();
     }