Add an assertion for the assumption that all identifier start characters are also valid continuation characters, so that we notice it if that ever changes.

Clean up the Lexicon.py generation script and use f-strings to prevent accidentally running it with older Python versions.

Closes #2601

* Fix coverage path search
* Add testcase

* Fix coverage path search
* Add testcase

Issue: #2541

Issue: #2541

Closes GH-2992.

Closes GH-2992.

I was going to use posix_madvise(POSIX_MADV_DONTNEED) in my tests to
make sure a memory page should be evicted from kernel cache, but found
out that this operation is hardcoded to be NOOP on Glibc/Linux systems:

https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/posix_madvise.c;h=c89fa64f0749;hb=HEAD#l25
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=8889e7aa461a

On the other hand, as also verified by strace, `madvise(MADV_DONTNEED)`
is not a NOOP as it actually goes to kernel by making syscall.

Since it is not possible to use posix_madvise for what should be
POSIX_MADV_DONTNEED behaviour, let's add all raw madvise behaviour flags
as documented on http://man7.org/linux/man-pages/man2/madvise.2.html

Presumably MADV_NORMAL and other behaviours that should translate 1-1 to
POSIX ones were omitted in 59ac9991 (Add pxd for mmap & friends
from "sys/mman.h" covering POSIX/Linux/BSD) to make people use the
standardised POSIX interface. However given that it turned out to be not
possible to use posix_madvise for all standard behaviours,
system-specific madvise behaviours have to be used.

(cherry picked from commit b394295b)

PyGILState_STATE was added in commit 3fd6fdce (Gilnanny + pystate.pxd)
with struct type on-purpose different from what CPython actually uses
with the idea so that PyGILState_STATE cannot be coerced into int.

However as it is, it prevents PyGILState_STATE usage:

	cdef PyGILState_STATE gstate = PyGILState_Ensure()

gives

	Variable type 'PyGILState_STATE' is incomplete

Fix it by making PyGILState_STATE a defined structure.

(cherry picked from commit 82a0ed43)

mmap returns void* and indicates failure via MAP_FAILED that is defined
to be ((void *)-1). Every mmap call has to be checked for failure and
thus posix.mman with mmap, but without MAP_FAILED is not very useful.

We cannot declare MAP_FAILED as enum, because enum assumes int. However
Cython documentation says

	4. If the header file uses macros to define constants, translate
	   them into a normal external variable declaration. ...

	(https://cython.readthedocs.io/en/latest/src/userguide/external_C_code.html#referencing-c-header-files)

So add proper declaration for MAP_FAILED to make posix.mman.mmap usable.

(cherry picked from commit 67253049)

mlock2 is Linux-specific version of mlock that accepts flags. The only
flag available so far is MLOCK_ONFAULT which asks to lock pages only at
the time when they are faulted in, not in the beginning. MCL_ONFAULT is
Linux-specific flag to mlockall which requests similar behaviour.

http://man7.org/linux/man-pages/man2/mlock2.2.html

(cherry picked from commit 83a5700b)