introduce LIBJ_TRACE
introduce LIBJ_USE_CLANG
introduce LIBJ_TRACE and LIBJ_USE_CLANG
refactor CMakeLists.txt
refactor CMakeLists.txt
refactor CMakeLists.txt
delete submodule 'googletest'
readd submodule 'googletest'
update submodule 'googletest'
delete an unused variable
move '#include <gc_cpp.h>'
include typedef.h
refactor detail::String
include console.h only if LIBJ_DEBUG is ON