Rework the usage of noskip_mask

Remove half of the masks since they are only used for cdef on a 8x8
level of granularity.

Load the mask and combine the 16-bit sections into the 32-bit sections
outside of the inner cdef loop. This should save some registers.

Results in mild performance improvements.
34 jobs for master in 4 minutes and 34 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Style
passed #520416
amd64 docker
style-check

00:00:06

passed #520417
amd64 docker
x86inc-check

00:00:06

 
  Build
passed #520428
amd64 docker
build-android-aarch64

00:00:11

passed #520427
amd64 docker
build-android-armv7

00:00:11

passed #520418
amd64 avx2 docker
build-debian

00:00:24

passed #520429
aarch64 docker
build-debian-aarch64

00:00:26

passed #520430
aarch64 docker
build-debian-aarch64-clang-5

00:00:26

passed #520433
armv7 docker
build-debian-armv7

00:00:45

passed #520434
armv7 docker
build-debian-armv7-clang-5

00:00:37

passed #520421
amd64 docker
build-debian-examples

00:00:18

passed #520436
ppc64le docker
build-debian-ppc64le

00:01:29

passed #520419
amd64 docker
build-debian-static

00:00:22

passed #520432
aarch64 docker
build-debian-werror

00:00:08

passed #520420
amd64 docker
build-debian32

00:00:33

passed #520431
catalina amd64
build-macos

00:00:36

passed #520435
amd64 docker
build-ubuntu-snap

00:00:32

passed #520425
amd64 docker
build-win-arm32

00:00:09

passed #520426
amd64 docker
build-win-arm64

00:00:12

passed #520422
amd64 docker
build-win32

00:00:42

passed #520423
amd64 docker
build-win32-unaligned-stack

00:00:26

passed #520424
amd64 docker
build-win64

00:00:56

 
  Test
passed #520437
amd64 docker
test-debian

00:00:54

97.8593%
passed #520446
aarch64 docker
test-debian-aarch64

00:00:34

passed #520448
armv7 docker
test-debian-armv7-clang-5

00:00:51

passed #520441
amd64 docker
test-debian-asan

00:01:23

passed #520438
avx2 amd64 docker
test-debian-asm

00:00:47

passed #520442
amd64 docker
test-debian-msan

00:00:36

passed #520447
ppc64le docker
test-debian-ppc64le

00:02:06

passed #520444
amd64 docker
test-debian-tsan

00:01:48

passed #520443
amd64 docker
test-debian-ubsan

00:01:31

passed #520440
amd64 avx2 docker
test-debian-unaligned-stack

00:00:30

passed #520439
avx2 amd64 docker
test-debian32-asm

00:01:02

passed #520484
docker avx2 amd64
test-win64

00:00:51

failed #520445
amd64 avx2 docker
test-win64

00:00:51