* Add POWER8 VSX toolchains

POWER8, though slower than POWER9, is still used in the wild; these
toolchains should still be much faster on POWER8 than POWER8 without VSX
optimizations.

* VSX toolchains: set -cpu arg in QEMU CI tests

* Add POWER9 VSX toolchains

Translating x86_64 SSE to ppc64le VSX intrinsics yields a quite large
speedup on POWER9. See this article for background:

https://www.talospace.com/2019/07/easier-power-vectorizing-for-fun-and.html

* Add power9le docs

* power9le clang toolchain: Document Clang 13+ requirement

---------

Co-authored-by: Jeremy Rand <jeremyrand@danwin1210.de>

* simplify binaryop

* less gpu test

* update binaryop broadcast doc

* do not test atan2 zero

* stb_image_write 1.16

* stb_image v2.28

* update emsdk 3.1.28

* enable stb arm neon

* update doc

Co-authored-by: ncnnnnn <67086033+ncnnnnn@users.noreply.github.com>

* mha is now permute and reshape free
* gemm user defined tile mnk param

* fix doc, sync x86 gemm fix

Co-authored-by: EdVince <EdVince@users.noreply.github.com>
Co-authored-by: nihuini <nihuini@tencent.com>

Co-authored-by: LRY89757 <LRY89757@users.noreply.github.com>
Co-authored-by: nihuini <nihuini@tencent.com>
Co-authored-by: nihui <shuizhuyuanluo@126.com>

* Add DeformableConv2D
* add unittest and docs
* pnnx torchvision deformconv2d conversion

Co-authored-by: miemie2013 <miemie2013@users.noreply.github.com>
Co-authored-by: nihui <shuizhuyuanluo@126.com>

Signed-off-by: Zhouzhou <1197236910@qq.com>

* Update release.yml

* Update how-to-build.md

- Translated Chinese documents into English
- Updated to VS2022 version

1. 🐛Fix Bug of float and int.  修复了std::max()中参数int和float参数不符合的Bug
2. 👀 The structure of ncnn changes.  ncnn文件结构变动,所有testlayer.cpp改成在tests/文件夹中

* basic mips msa optimization for convolution int8

* mips msa optimization for convolution int8 gemm

* mips msa optimization for convolution int8 winograd pack8to4/pack8to1

* mention msa maddv/msubv intrinsics bug

Co-authored-by: MegEngine <megengine@megvii.com>