Enforced strict error on malformed self-closing tag.

[springcomp]

Fixes #109.

This pull request ensures that malformed self-closing tags are reported.

To solve this issue, the XmlTagState handler looks into the context.Statetag value MAYBE_SELF_CLOSING.
In that case, no other characters than > are accepted.

I noticed that the current code has the same value for two different state tags.
Essentially, I changed the assignments like thus:

		const int ATTEMPT_RECOVERY = 1;
		const int RECOVERY_FOUND_WHITESPACE = 2;
-		const int MAYBE_SELF_CLOSING = 2;
+		const int MAYBE_SELF_CLOSING = 3;
		const int FREE = 0;

I’m not sure what other impacts this has on the code, but all unit-tests are green, so 🤷.