* [LITE][OPENCL] Change fp32 fc to fp16's. test=develop

* fix act in conv3x3opt opencl kernel. test=develop

* [LITE][DEMO] Enhance mobile_light demo. test=develop

* fix print. test=develop

* fix clang v7 error
* change ut, test=develop
* fix conv ut, test=develop

* [Core] Fix findar for Clang
test=develop

* [CORE] Fix the missing of feed and fetch kernel when using light API to loade the optimized model
test=develop

* add mean op, test=develop

* split forward and backward, test=develop

add pad2d image kernel and ut

* feat: add dropout opencl kernel

* fix v7 clang bug. test=develop

* fix format, test=develop

* fix .a build bug, test=develop

* [NPU] revert shape check for input&output

* [NPU] reshape elt input&output

* feat: add opencl elementwise_sub op & ut

* fix clang compile armv8 cpu 's shared lib. test=develop

* use build-in shared helper function. test=develop

add instance norm kernel and ut

* set arm_lang default is off. test=develop

* fix resize error, test-develop

* add lookup_dequant_op

* feat: add opencl elementwise_sub op & ut

* enhance gather, lookup_table arm kernel uts

* enhance beam_search, beam_search_decoder, increment rigster

[LITE][OPENCL][Image] revert router of depthwisespl --> fix mnasnet and nanoyolo ,test=develop (#3109)

* [CORE] Support Clang compiling for Android
test=develop

* fix lto for jni so
test=develop

* disable assembly code
test=develop

* disable layout.cc
test=develop

* refine
test=develop

* Enable LTO on Clang
test=develop

* Disable LTO when clang is used.
test=develop

* Remove space
test=develop

* [Core] enable clang in build.sh
test=develop

* [Core] Remove the workaround for clang compiling
test=develop

* add lrn op

* fix v7 build error, test=develop

* [LITE][CMAKE] support clang compile for armv8 cpu. test=develop

* add build for clang. test=develop

* fix cmake format. test=develop