Add regression test for exponential complexity of recursive imports
Fix exponential complexity of recursive imports
Remove logging code which has a detrimental performance impact on processing recursive imports
Suppress OPTIONS_IN_DELEGATE warning if all options match the root grammar (fixes #707)
Deprecate ALL_OPS_NEED_SAME_ASSOC (fixes #652)
Add regression test for #670
NullUsageProcessor supports Java 6 through 8 (fixes #487)
Add Parser.isTrace() (fixes #701)
Fix JDK8 incompatible comments

In JDK8 javadoc runs a lint pass over the documentation and fails if the docs
are not valid HTML. Also, see following article for a more in-depth 
discussion (http://blog.joda.org/2014/02/turning-off-doclint-in-jdk-8-javadoc.html)

Removed all occurrences of <br />,<p /> and replaced them with <br> and
<p>.
Merge pull request #714 from sharwell/fix-652

Deprecate ALL_OPS_NEED_SAME_ASSOC
Merge pull request #717 from sharwell/fix-701

Add Parser.isTrace()
Merge pull request #716 from sharwell/fix-670

Add regression test for #670
Merge pull request #715 from sharwell/fix-487

NullUsageProcessor supports Java 6 through 8
Merge pull request #713 from sharwell/fix-707

Improved support for recursive imports
Extract abstract model class Recognizer (parent of Parser and Lexer)
Implement token vocabulary (fixes #711)
Fix test compile error by avoiding string literal assignments for the large lexer test
Allow XPath matching by literal or symbolic name (fixes #579)
indentation fix
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