Speedups: remove dependency on c++ (#2796)

* Speedups: remove dependency on c++

* Speedups: intset: handle malloc failing

* Speedups: intset: fix corner case for int64 on 32bit systems

original idea was to only use bucket->val if int<pointer,
but we always have a union now anyway

* Speedups: add size comment to player_set bucket configuration

* test: more tests for LocationStore.find_item

* test: require _speedups in CI

This kind of tests that the build succeeds.

* test: even more tests for LocationStore.find_item

* Speedups: intset uniform comment style

* Speedups: intset: avoid memory leak when realloc fails

* Speedups: intset: make `gcc -pedantic -std=c99 -fanalyzer` without warnings

Unnamed unions are not in C99, this got fixed.
The overhead of setting count=0 is minimal or optimized-out and silences -fanalizer (see comment).

* Speedups: don't leak memory in case of exception

* Speedups: intset: validate alloc and free

This won't happen in our cython, but it's still a good addition.

* CI: add test framework for C/C++ code

* CI: ctest: fix cwd

* Speedups: intset: ignore msvc warning

* Tests: intset: revert attempt at no-asan

We solve this with env vars in ctest now, and this fails for msvc.

* Test: cpp: docs: fix typo

* Test: cpp: docs: fix another typo

* Test: intset: proper bucket count for Negative test

INTxx_MIN % 1 would not produce a negative number, so the test was flawed.

_speedups.pyxbld

@@ -1,8 +1,10 @@
-# This file is required to get pyximport to work with C++.
-# Switching from std::set to a pure C implementation is still on the table to simplify everything.
+# This file is used when doing pyximport
+import os
 
 def make_ext(modname, pyxfilename):
     from distutils.extension import Extension
     return Extension(name=modname,
                      sources=[pyxfilename],
-                     language='c++')
+                     depends=["intset.h"],
+                     include_dirs=[os.getcwd()],
+                     language="c")