vkimagemat was originally used as a mat storage in the hope of improving performance on old adreno gpus, but in fact it is slower than the cpu in most cases and is no longer suitable for the latest adreno architecture and large shapes
* query subgroup features
* compile spirv 1.3
* drop offline spirv build
* do not build tests for android and ios, as they are never tested anyway
* code style
* [build] add toolchain file w/o stdcxx dependency
* [build] link m and gcc lib explicitly
* [ncnn] complete simple stl impl
* [ncnn] adapt for ncnn simplestl
* [test] adapt for ncnn simplestl
* [ncnn] fix missing algorithm and list when simplestl disabled
* [ncnn] fix guard for operator new and delete
* [style] fix the code style
* [build] fix build failed on darwin and emscripten
* [ci] do not import cxx to avoid operator conflict
* [ncnn] add temporary partial_sort impl using bubble sort
heap sort should be used for better perf.
* [ncnn] add std greater and less function
* [ncnn] fix placement new operator overload
* [ncnn] add operator delete with size info
* [build] disable exception, rtti, example and tools when simplestl on
* [build] add toolchain for arm simplestl
* [build] add toolchain for aarch64 simplestl
* [ncnn] move initializer to constructor
* [ncnn] use deteiled type instead of auto
* [ncnn] use plain lib name in target_link_libraries
nihui