Do not apply decorators twice

DOC: Add calls to Py_Initialize/Py_Finalize in code sample.

propagate "const char*" that Py3.7 returns from PyUnicode_AsStringAndSize() to user code and make the casts to "char*" explicit for each assignment/conversion
see https://bugs.python.org/issue28769

see https://bugs.python.org/issue28769

fused types: also ignore numpy import failures and not only failed lookups of the ndarray type (both just let ndarrays be ignored further on)

This fixes #1739.

Automatically add include_dirs for externs

This fixes #1737.

This avoids issues of having to inject/name them
(and any conversions, see e.g. Issue #1737).

Trivial: fix link in docs

This fixes the regression at #1706 and will become an error with #1736.

Mention class name in error messages

This fixes #1732.

This was identical to tests/errors/cmethbasematch.pyx

safety fix: do not access type struct field "tp_finalize" if the type states that it does not have it (because the struct might really be shorter in that case)

Repair syntax test after fixing github issue #1726, which also made "continue" a syntax error outside of loops in try-except blocks.