DJGPP adjustments

* Configure: Replaced -DTERMIO by -DTERMIOS in CFLAGS.

* crypto/bio/bss_dgram.c [WATT32]: Remove obsolete redefinition of
  function names: sock_write, sock_read and sock_puts.

* crypto/bio/bss_sock.c [WATT32]: For Watt-32 2.2.11 sock_write,
  sock_read and sock_puts are redefined to their private names so
  their names must be undefined first before they can be redefined
  again.

* crypto/bio/bss_file.c (file_fopen) [__DJGPP__]: Make a copy of the
  passed file name and replace the leading dots in the dirname part
  and the basname part of the file name, unless LFN is supported.

* e_os.h [__DJGPP__]: Undefine macro DEVRANDOM_EGD. Neither MS-DOS nor
  FreeDOS provide 'egd' sockets.
  New macro HAS_LFN_SUPPORT checks if underlying file system supports
  long file names or not.
  Include sys/un.h.
  Define WATT32_NO_OLDIES.

* INSTALL.DJGPP: Update URL of WATT-32 library.

Submitted by Juan Manuel Guerrero <juan.guerrero@gmx.de>

RT#4217

Reviewed-by: Andy Polyakov <appro@openssl.org>