Fix implementation of BCD mode quirks on 6502 and 65c02#56

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KrisKennaway wants to merge 20 commits intomnaberez:mainfrom

KrisKennaway:decimal

Commits on May 10, 2017

Test harness for executing Klaus Dormann's 6502-based test suites, see
KrisKennaway
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Merge branch 'master' of https://github.com/mnaberez/py65
User Apple2
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Commits on May 11, 2017

Add support for optionally tracing execution
KrisKennaway
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Support tracing execution for particular PC values. Use this to
KrisKennaway
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Use the decimally adjusted aluresult to compute the value of flags.
KrisKennaway
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Commits on Jul 22, 2017

Commits on Aug 20, 2019