Fixed error range for EntityNotDeclared

[angelozerr]

Given this XML file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article [
  <!ELEMENT article (#PCDATA)>
]>          
<article>
	&nbsp;
</article>

  should be highlighted. (It should be managed in XMLSyntaxErrorCode).

CodeAction could create the proper entity in the DOCTYPE like this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article [
  <!ELEMENT article (#PCDATA)>
  <!ENTITY nbsp "entity-value">
]>           
<article>
	&nbsp;
</article>

We must take care of existing of doctype. For instance if we have

<?xml version="1.0" encoding="UTF-8"?>          
<article>
	&nbsp;
</article>

CodeAction should generate

<!DOCTYPE article [
  <!ENTITY nbsp "entity-value">
]>

[fbricon]

Error range fix has been merged. Code action will be handled in #532