RT #90792: PPI::XSAccessor overwrites indexing of actual source modules on CPAN

This commits hides the packages in XSAccessor from the CPAN indexer and
should thus enable metacpan to link docs and source of PPI modules
correctly.
RT# 69026: PPI docs mention PPI::Token::Bareword, but it does not exist

The PPI docs showed an example tree structure supposedly generated by
parsing some Perl document, but the example had gotten out of synch with
reality, showing two element types that don't actually exist.

This commit fixes that by replacing the erroneous element classes with
those actually parsed.
typo fixes
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Merge pull request #6 from dsteinbrunner/patch-1

typo fixes
Merge pull request #3 from adamkennedy/inaccurate_PDOM_examples

RT# 69026: PPI docs mention PPI::Token::Bareword, but it does not exist
Merge pull request #2 from adamkennedy/xsaccessor_shadowing_fix

RT #90792: PPI::XSAccessor overwrites indexing of actual source modules on CPAN