Add two tests that are hitting the assert.
Names starting with a colon are valid according to the spec, but the spec also recommends that they only be used for namespaces. To allow proper error recovery we simplify and do not accept colons in names.
This is the XML language service from MonoDevelop. It has been
extracted and the MonoDevelop dependencies have been removed. The parser has no external dependencies, and
the code completion has been ported to the Visual Studio Editor core.