Issue #3605: enable certain SAXParserFactory features.

[liutikas]

Issue #3605: enable certain SAXParserFactory features.

[codecov-io]

Current coverage is 99.59% (diff: 100%)

Merging #3614 into master will increase coverage by <.01%

@@             master      #3614   diff @@
==========================================
  Files           275        275          
  Lines         13310      13312     +2   
  Methods           0          0          
  Messages          0          0          
  Branches       3034       3034          
==========================================
+ Hits          13256      13258     +2   
  Misses           53         53          
  Partials          1          1          

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[rnveach]

@liutikas CI is failing because of improper commit message by our rules.
Please see https://travis-ci.org/checkstyle/checkstyle/jobs/181539876#L828-L837 and correct according.

Also please squash all commits and keep as 1.

[liutikas]

@rnveach I updated the commit message and squashed the commits.

I looked at "IDEA Inspections Pull Request" check and it seems that I did not add any new warnings. I am not sure why it is failing.

[rnveach]

@romani It looks like IDEA updated to newest IntelliJ version. 1255 errors, 2381 total.
@liutikas Please ignore IDEA as I believe this is unrelated to your change.

[romani]

@liutikas , IDEA could be ignored by you in this PR.
Please explain in issue a reason of second feature that you enabled. We need more details as we can not completely recheck your requests so we need all possible details to explain this code. There might appear some conflict of interests in future, so details are required.

[liutikas]

Sure thing, both features load-external-dtd and external-general-entities are normally default set to true. Our company has set their java defaults to false as it can lead to cross scripting attacks if not handled correctly. load-external-dtd feature allows to load external DTD into a an XML document and external-general-entities feature allows to these these external DTDs in elements. Using these two we are able to compose configuration files from multiple XML files. Since both of these features are enabled by default in default java set ups it should be a no-op for most checkstyle users.

[romani]

reason was moved to issue.