slight refactoring of show_backtrace to allow it to be used outside the REPL
rm redundant ptrint_t typedef
add licenses, for libraries bundled with windows dist, to LICENSE.md
signal_stack doesn't apply to windows. fix #3816
cleanup some stack walking code
fix for missing libunwind header in julia.h
attempt fix again for missing libunwind header
Merge github.com:JuliaLang/julia