* build shared lib and enable lto

* reserved for layer and option

* allocator pimpl

* datareader pimpl

* paramdict pimpl, disable copy assign for allocator and datareader

* modelbin pimpl

* net extractor pimpl

* gpu pimple

* disable copy assign vulkandevice, code format

* command pimpl, dummy image readonly

* pipeline pipelinecache pimpl, export platform class

* code format, export simple family

* update ci

* disable lto on android armv7, merge webassembly ci

* link libgcc, fix macos dylib version

* pipeline pimpl, gpu info pimpl

* destroy gpu info after vulkan device

* ignore msvc stl class warning

* fix ncnn_paramdict_get_float return type

* fix vktransfer upload fp16 without flatten, add command test

* cmake option for platform api uses
* adroid gpu ci does not rely on glslangvalidator, add android termux ci

* Change DataReader::read()'s signature to fix warning C4267

This CL fixes lots of warning "C4267: 'initializing': conversion from
'size_t' to 'int'" in our codebase by matching DataReader::read()'s
signature to fread().

* Fix warnings C4244 and C4267 in tools/ncnnoptimize.cpp

C4244: 'initializing': conversion from 'double' to 'float',
    possible loss of data
C4267: 'initializing': conversion from 'size_t' to 'int',
    possible loss of data

* Fix warning C4244 in src\layer\selu.cpp

C4244: '=': conversion from 'double' to 'float', possible loss of data

* Fix warning C4244 in src\layer\cast.cpp

C4244: '=': conversion from 'double' to 'float', possible loss of data
C4244: 'return': conversion from 'float' to 'signed char', possible loss of data

* Fix warning C4244 in src\layer\psroipooling.cpp

C4244: 'initializing': conversion from 'double' to 'float',
    possible loss of data
C4244: 'initializing': conversion from 'double' to 'int',
    possible loss of data