Use dup2 if available for -t. Also check for ttyname and isatty in configure.

Use dup2 if available for -t. Also check for ttyname and isatty in configure.

	* configure.ac: Add some additional functions to check and add the
	HAVE_ISATTY and HAVE_TTYNAME

	* src/emacs.c (main_1): Enhance the logging of -t with ttyname if
	it is available.

	* src/emacs.c (main_1): Use raw_open instead of open to avoid
	using the format conversion of the filename, which at this early
	stage is not setup yet.

	* src/emacs.c (main_1): use dup2 if available to dup the opened
	file (and then close the original descriptor). This is much more
	reliable than close then open, since dup2 will make sure the
	descriptor number will be the desired.

	* src/eval.c (grow_specpdl): If grow_specpdl is called very early
	on specpdl_size is 0 and will loop infinitely here because 2 * 0
	== 0 ;)

	* src/sysdep.c (raw_open): New function that just calls the system
	open with no argument conversion at all

	* src/sysfile.h: declare the new raw_open function.

Signed-off-by: Nelson Ferreira <nelson.ferreira@ieee.org>