Improve Windows Console I/O

- Blocking read operations on the Windows Console can now EINTR
- Blocking read operations on Windows pipes now EINTR more reliably
- setitimer() will no longer be inherited across fork() on Windows
- It's now possible to use ECHO when the console is in raw mode
- The ECHOCTL flag now works correctly on the Windows Console
- The ICRNL flag now works correctly on the Windows Console
- pread() and pwrite() will now raise ESPIPE on Windows
- Opening /dev/tty on Windows is improved (untested)
- Overlapped I/O is now implemented in a better way

libc/stdio/fgetln.c

@@ -30,6 +30,9 @@
  * The returned memory is owned by the stream. It'll be reused when
  * fgetln() is called again. It's free()'d upon fclose() / fflush()
  *
+ * When reading from the console on Windows in `ICANON` mode, the
+ * returned line will end with `\r\n` rather than `\n`.
+ *
  * @param stream specifies non-null open input stream
  * @param len optionally receives byte length of line
  * @return nul-terminated line string, including the `\n` character

libc/stdio/fgets.c

@@ -26,6 +26,9 @@
  * exceeding size. The line ending marker is included and may be removed
  * using _chomp().
  *
+ * When reading from the console on Windows in `ICANON` mode, the
+ * returned line will end with `\r\n` rather than `\n`.
+ *
  * @param s is output buffer
  * @param size is capacity of s
  * @param f is non-null file object stream pointer

libc/stdio/getline.c

@@ -33,13 +33,16 @@
  * documentation. Concerning lines, please note the \n or \r\n are
  * included in results, and can be removed with _chomp().
  *
- * @param line is the caller's buffer (in/out) which is extended
- *     automatically. *line may be NULL but only if *n is 0;
+ * When reading from the console on Windows in `ICANON` mode, the
+ * returned line will end with `\r\n` rather than `\n`.
+ *
+ * @param linebuf is the caller's buffer (in/out) which is extended
+ *     automatically. *line may be NULL but only if *capacity is 0;
  *     NUL-termination is guaranteed FTMP
  * @return number of bytes read, including delim, excluding NUL, or -1
  *     w/ errno on EOF or error; see ferror() and feof()
  * @see fgetln(), xgetline(), getdelim(), gettok_r()
  */
-ssize_t getline(char **line, size_t *n, FILE *f) {
-  return getdelim(line, n, '\n', f);
+ssize_t getline(char **linebuf, size_t *capacity, FILE *f) {
+  return getdelim(linebuf, capacity, '\n', f);
 }