* config/i386/mingw.mh, config/i386/mingw.mt: New files.

	* config/i386/mingw.mh, config/i386/mingw.mt: New files.
	* configure.tgt	(i[34567]86-*-mingw32*): Set gdb_target = mingw.
	* win32-nat.c: Only include cygwin.h on Cygwin host.  Don't
	include procfs.h.
	(cygwin_load_start, cygwin_load_end, cygwin_exceptions): Disable
	if not building on Cygwin.
	(win32_make_so, handle_output_debug_string, handle_exception)
	(do_initial_win32_stuff): Wrap Cygwin specific code in __CYGWIN__.
	(win32_attach): Only fallback to Cygwin pids if building on
	Cygwin.
	(win32_pid_to_exec_file): Disable Cygwin specific code, if not
	building on Cygwin.
	(win32_create_inferior): Disable starting the inferior through a
	shell, environment var processing and tty handling if not building
	on Cygwin.
	(cygwin_pid_to_str): Rename to ...
	(win32_pid_to_str): ... this.
	(init_win32_ops): Update use of win32_pid_to_str.  Disable "shell"
	and "cygwin-exceptions" commands if not building on Cygwin.