Remove Stackless hack for looking up "PyFrameObject.f_localsplus" from Stackless 3.8 on. CPython never needed this.

Closes https://github.com/cython/cython/issues/4329

See https://github.com/cython/cython/issues/4310

See https://github.com/cython/cython/issues/4310

This creates two copies of the function, one for the exception
case and one for the non-exception case. It's probably inefficient
but the simplest solution.

Fixes https://github.com/cython/cython/issues/4651.

This creates two copies of the function, one for the exception
case and one for the non-exception case. It's probably inefficient
but the simplest solution.

Fixes https://github.com/cython/cython/issues/4651.

Closes https://github.com/cython/cython/issues/4655

Add a "minimal compile" build mode that speeds up the compiler somewhat but keeps the number of compiled modules low.

runtests: Print shard number also for each command in the EndToEnd test error output to make it easy to find in the logs.

runtests: print the shard number in front of the test name to show which was the last test in case it hangs.

See https://github.com/cython/cython/pull/4583#issuecomment-1036452181

Fixes https://github.com/cython/cython/issues/4092

Nested cdef classes are not tested because they don't officially work
at this stage (see https://github.com/cython/cython/issues/4572).
It should be tested if/when they're fully supported.

Limited API: Fix line number reporting in tracebacks that accidentally used 'c_line' instead of 'py_line'. In fact, we cannot currently show the C line, so disable C line reporting completely here.

Follow PEP-484 and warn about "func(x: list = None)" without an explicit "typing.Optional[]" declaration.

See https://github.com/cython/cython/issues/3883

Avoid an unnecessary inefficiency in a regex, although it is not relevant in practice since the regex is only applied to Cython's only C code.
Found by GitHub CodeQL.

Rewrite the section that describes the differences between __cinit__() and __init__(), to make it clearer when to use which.