Make improvements for Actually Portable Emacs

- Get SIGWINCH working again on the New Technology
- Correctly handle O_NOFOLLOW in open() on Windows
- Implement synthetic umask() functionality on Windows
- Do a better job managing file execute access on Windows
- Fill in `st_uid` and `st_gid` with username hash on Windows
- Munge UNICODE control pictures into control codes on Windows
- Do a better job ensuring Windows console settings are restored
- Introduce KPRINTF_LOG environment variable to log kprintf to a file

libc/calls/stat.c

@@ -20,19 +20,14 @@
 #include "libc/sysv/consts/at.h"
 
 /**
- * Returns information about thing.
+ * Returns information about file.
  *
- * @param st is where result is stored
- * @see S_ISDIR(st.st_mode), S_ISREG(), etc.
- * @raise EACCES if denied access to component in path prefix
- * @raise EIO if i/o error occurred while reading from filesystem
- * @raise ELOOP if a symbolic link loop exists in `path`
- * @raise ENAMETOOLONG if a component in `path` exceeds `NAME_MAX`
- * @raise ENOENT on empty string or if component in path doesn't exist
- * @raise ENOTDIR if a parent component existed that wasn't a directory
- * @raise EOVERFLOW shouldn't be possible on 64-bit systems
- * @raise ELOOP may ahappen if `SYMLOOP_MAX` symlinks were dereferenced
- * @raise ENAMETOOLONG may happen if `path` exceeded `PATH_MAX`
+ * This function is equivalent to:
+ *
+ *     struct stat st;
+ *     fstatat(AT_FDCWD, path, &st, 0);
+ *
+ * @see fstatat() for further documentation
  * @asyncsignalsafe
  */
 int stat(const char *path, struct stat *st) {