rt: add #define's to reduce unnecessary includes from windows.h
std: fix path_is_dir and path_exists on Windows.
std: fix getcwd on Windows. (#9618)
rt: fix rust_localtime on Windows. (#9418)
use _wstat instead of GetFileAttributesW due to failure to check system files.
rt: add comments
std: remove unused consts and an extern function.
add some comments.
std: add tests for unicode path on Windows
std: fix according to new Path
std: fix build error (including on x86_64), make libc pretty