Make tracing tests work exactly as in CPython and compare the tracing results for both Python and Cython functions.
Fix "frame.f_trace" test in tracing code accordingly.
See #1769 and #1774 for background.

Better fix for #1836: set frame flags to make CPython create a new dict for "frame.f_locals" at need.

Pass am empty dict instead of a f_globals reference to profilers.

See #1774.

Fix "NoneType object is not callable" exception when using a tracing …

travis: disable dependency installation in "-dev" Python builds (currently fails for Py3.7, and might fail again in the future).

Partial workaround for Github Issue #1852.

Evaluate and join more f-string constants at compile time, including unprefixed strings.
Fix a case where f-string constants could have incorrect constant compile time result values, thus leading to incorrect comparisons and constant folding errors.

Implement two more special cases in fstring joining to reduce the need for runtime character size detection.

Add wheelhouse directories to gitignore.

Remove support and special handling code for Py3.2.

Try to include some more test dependencies in the travis build (but exclude them in Py2.6, which is often no longer supported already).

Include PySet_Check and PyFrozenSet_Check to CPython includes file