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.

Closes #1726.

Fix a compiler crash when casting to a memoryview

Allow pointer access to 64-bit arrays

Here the residue always fits into an int.  This fixes #1721.

Limit Python conversion on attribute access.

When not imported, this caused was a runtime NameError.  Now an error
is given at compile time.

Support parsing of named Unicode escapes outside of the BMP in CPythons versions with a 2-byte Unicode representation.
Closes #1693.