pyx.build: Fix build after Cython 3 release

Unfortunately the best Cython release ever[1] breaks build for Pygolang[2], and
people on the net also report that there are other problems - both build
failures and popped up performance problems due to changed semantic[3,4,...].

Fix it all on Pygolang side by, for now, not delving into being Cython 3
beta-testers and relying on field-proven Cython 2.

/reported-by @levin.zimmermann

[1] https://groups.google.com/g/cython-users/c/o41CrcRkVvo
[2] wendelin.core!16 (comment 188623)
[3] https://news.ycombinator.com/item?id=36778617
[4] https://github.com/cython/cython/issues/5540
102 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed Pygolang.UnitTest-Master.Python2

00:01:18

failed Pygolang.UnitTest-Master.Python3

00:01:44

passed Pygolang.UnitTest-Master.Python2

00:01:35

failed Pygolang.UnitTest-Master.Python2

00:01:54

passed Pygolang.UnitTest-Master.Python2

00:01:41

passed Pygolang.UnitTest-Master.Python2

00:01:44

passed Pygolang.UnitTest-Master.Python2

00:01:33

passed Pygolang.UnitTest-Master.Python2

01:07:47

failed Pygolang.UnitTest-Master.Python2

00:02:58

failed Pygolang.UnitTest-Master.Python2

00:01:38

passed Pygolang.UnitTest-Master.Python2

00:01:22

passed Pygolang.UnitTest-Master.Python2

00:01:27

passed Pygolang.UnitTest-Master.Python2

00:01:47

passed Pygolang.UnitTest-Master.Python2

00:01:41

passed Pygolang.UnitTest-Master.Python2

00:01:27

passed Pygolang.UnitTest-Master.Python2

00:02:09

passed Pygolang.UnitTest-Master.Python2

00:01:38

passed Pygolang.UnitTest-Master.Python2

00:01:15

passed Pygolang.UnitTest-Master.Python2

00:01:40

passed Pygolang.UnitTest-Master.Python2

00:01:42

passed Pygolang.UnitTest-Master.Python2

00:01:53

failed Pygolang.UnitTest-Master.Python2

00:02:03

passed Pygolang.UnitTest-Master.Python2

00:01:34

passed Pygolang.UnitTest-Master.Python2

00:01:36

failed Pygolang.UnitTest-Master.Python2

00:01:56

failed Pygolang.UnitTest-Master.Python2

00:02:13

passed Pygolang.UnitTest-Master.Python2

00:01:30

passed Pygolang.UnitTest-Master.Python2

00:01:46

passed Pygolang.UnitTest-Master.Python2

00:01:50

passed Pygolang.UnitTest-Master.Python2

00:01:18

passed Pygolang.UnitTest-Master.Python2

00:01:20

failed Pygolang.UnitTest-Master.Python2

00:01:54

passed Pygolang.UnitTest-Master.Python2

00:01:41

passed Pygolang.UnitTest-Master.Python2

00:01:20

passed Pygolang.UnitTest-Master.Python2

00:01:22

passed Pygolang.UnitTest-Master.Python2

00:01:55

passed Pygolang.UnitTest-Master.Python2

00:01:32

passed Pygolang.UnitTest-Master.Python2

00:01:39

passed Pygolang.UnitTest-Master.Python2

00:01:32

passed Pygolang.UnitTest-Master.Python2

00:01:27

passed Pygolang.UnitTest-Master.Python2

00:01:33

passed Pygolang.UnitTest-Master.Python2

00:01:37

passed Pygolang.UnitTest-Master.Python2

00:59:01

passed Pygolang.UnitTest-Master.Python2

00:01:16

passed Pygolang.UnitTest-Master.Python2

00:01:41

passed Pygolang.UnitTest-Master.Python2

00:01:20

passed Pygolang.UnitTest-Master.Python2

00:01:25

passed Pygolang.UnitTest-Master.Python2

00:01:22

failed Pygolang.UnitTest-Master.Python2

00:01:43

passed Pygolang.UnitTest-Master.Python2

00:01:17

passed Pygolang.UnitTest-Master.Python2

00:01:34

failed Pygolang.UnitTest-Master.Python2

00:01:17

failed Pygolang.UnitTest-Master.Python3

00:01:58

failed Pygolang.UnitTest-Master.Python3

00:02:14

failed Pygolang.UnitTest-Master.Python3

00:02:26

failed Pygolang.UnitTest-Master.Python3

00:01:50

failed Pygolang.UnitTest-Master.Python3

00:02:08

failed Pygolang.UnitTest-Master.Python3

00:03:19

failed Pygolang.UnitTest-Master.Python3

00:01:52

failed Pygolang.UnitTest-Master.Python3

00:01:53

failed Pygolang.UnitTest-Master.Python3

00:02:53

failed Pygolang.UnitTest-Master.Python3

00:02:44

failed Pygolang.UnitTest-Master.Python3

00:02:38

failed Pygolang.UnitTest-Master.Python3

00:02:03

failed Pygolang.UnitTest-Master.Python3

00:02:24

failed Pygolang.UnitTest-Master.Python3

00:01:55

failed Pygolang.UnitTest-Master.Python3

00:02:34

failed Pygolang.UnitTest-Master.Python3

00:02:20

failed Pygolang.UnitTest-Master.Python3

00:02:54

failed Pygolang.UnitTest-Master.Python3

00:01:50

failed Pygolang.UnitTest-Master.Python3

00:03:06

failed Pygolang.UnitTest-Master.Python3

00:02:11

failed Pygolang.UnitTest-Master.Python3

00:01:50

failed Pygolang.UnitTest-Master.Python3

00:47:47

failed Pygolang.UnitTest-Master.Python3

00:02:04

failed Pygolang.UnitTest-Master.Python3

00:01:42

failed Pygolang.UnitTest-Master.Python3

00:02:30

failed Pygolang.UnitTest-Master.Python3

00:02:45

failed Pygolang.UnitTest-Master.Python3

00:02:31

failed Pygolang.UnitTest-Master.Python3

00:02:18

failed Pygolang.UnitTest-Master.Python3

00:02:21

failed Pygolang.UnitTest-Master.Python3

00:01:40

failed Pygolang.UnitTest-Master.Python3

00:02:00

failed Pygolang.UnitTest-Master.Python3

00:02:00

failed Pygolang.UnitTest-Master.Python3

00:01:03

failed Pygolang.UnitTest-Master.Python3

00:02:10

failed Pygolang.UnitTest-Master.Python3

00:02:13

failed Pygolang.UnitTest-Master.Python3

00:02:21

failed Pygolang.UnitTest-Master.Python3

00:02:25

failed Pygolang.UnitTest-Master.Python3

00:01:56

failed Pygolang.UnitTest-Master.Python3

00:01:37

failed Pygolang.UnitTest-Master.Python3

00:01:39

failed Pygolang.UnitTest-Master.Python3

00:01:42

failed Pygolang.UnitTest-Master.Python3

00:01:45

failed Pygolang.UnitTest-Master.Python3

00:01:49

failed Pygolang.UnitTest-Master.Python3

00:53:17

failed Pygolang.UnitTest-Master.Python3

00:01:41

failed Pygolang.UnitTest-Master.Python3

00:01:48

failed Pygolang.UnitTest-Master.Python3

00:01:42

failed Pygolang.UnitTest-Master.Python3

00:01:48

failed Pygolang.UnitTest-Master.Python3

00:01:34

failed Pygolang.UnitTest-Master.Python3

00:01:34