Merge branch 'grubba/pty-handling' into 8.0

* grubba/pty-handling:
  Process [NT]: Fixed typo in previous commit.
  Process [NT]: Support UTF-8 in create_process().
  I/O [NT]: Added low_dwim_utf8_to_utf16().
  I/O [NT]: Fixed some typos.
  I/O [NT]: Added dynamic lookup of symbols needed for pty handling.
  I/O [NT]: Added fallbacks for some stuff needed for pty handling.
  Build [Stdio]: Make systems without termios.h (ie NT) happy again.
  Stdio: Make Coverity happy. [CID 1457890]
  Stdio: Fixed some inverted tests in my_openpty().
  Stdio: Removed extraneous and broken #include of <pty.h>.
  Stdio: Added support for PROP_TTY to pipe().
  Stdio: Some pty-handling cleanup.