Fix -hideAnnotation

-hideAnnotation was not listed in optionLength(String), so Javadoc would
reject it as an invalid parameter.

Test: Sadly, there are no unit tests for Doclava right now,
but I modified a build to use the new option and verified everything built.
Change-Id: Iefa0b0416519221b385ce52156a6677ea55a530a
1 file changed