* check in initial version of linux build documents
* update en/build/linux.md
* remove line break
* update build doc
* check in build documents in Chinese
* reorg chapter
* update build documents for windows platform
* update zh_cn/windows.md
* simplify build commands
* update build docs
* update build.md
* update
* reorg the chapters
* refine words
* correct the commands for windows build
* correct build commands for windows
* Trim Trailing Whitespace
* use prebuilt cmake instead of building it from source
* move <br> bewtween <pre><code> and </code></pre> cuz it isn't rendered correctly in github
* add build chapter about torchscript
* rebase master and update android
* fix lint
* correct the command of building ppl.cv
* fix different dims and data sync and fp16 macro
* fix pad is negative bug, but still need debugging info
* split detection_output to dets and labels
* fix clang++ compile bug
* for fp16 compile macro of cmake
* fix pad_val dict input
* fix yolox missing normalization and get int tensor
* about score_threshold
* remove -lstdc++fs for android
* move -pthread for android
* fix link libraries for CLANG++;
* fix clang-format
* for mobileyolov3 conf_thre
* fix lint
* fix bug
* support ncnn vulkan net
* remove unused debugging info;
* Change INFO to DEBUG
* support vulkan precision mapping
* fix pad
* optimize getdetslabels
* remove EVAL_MODE
* ncnn_net support 4-dim data.
* remove FP16 compile options
* remove use_gpu_vulkan compile options
* fix pad.cpp
* fix yapf
* fix clang-format
* rm redundant lines
* fix pad according to mmdet
* add android build docs
* fix lint
* use cpp style string comparision
* fix use after free bug
* Add missing -DBUILD_SHARED_LIBS=OFF for en
* Add missing -DBUILD_SHARED_LIBS=OFF for ZH-CN
* reset img2tensor_impl
* reset img2tensor_impl
* add blank line
* sync android.md docs
* fix some dirs
* fix docs
* update docs
* fix code