* security.h: Declare internal_getpwsid and internal_getgrsid.

	* security.h: Declare internal_getpwsid and internal_getgrsid.
	Undeclare internal_getpwent.  Define DEFAULT_UID_NT.  Change
	DEFAULT_GID.
	* passwd.cc (internal_getpwsid): New function.
	(internal_getpwent): Suppress.
	(read_etc_passwd): Make static.  Rewrite the code for the completion
	line.  Set curr_lines to 0.
	(parse_pwd): Change type to static int.  Return 0 for short lines.
	(add_pwd_line): Pay attention to the value of parse_pwd.
	(search_for): Do not look for nor return the DEFAULT_UID.
	* grp.cc (read_etc_group): Make static.  Free gr_mem and set
	curr_lines to 0.  Always call add_pwd_line.  Rewrite the code for the
	completion line.
	(internal_getgrsid): New function.
	(parse_grp): If grp.gr_mem is empty, set it to &null_ptr.
	Never NULL gr_passwd.
	(getgrgid32): Only return the default if ntsec is off and the gid is
	ILLEGAL_GID.
	* sec_helper.cc (cygsid::get_id): Use getpwsid and getgrsid.
	(cygsid_getfrompw): Clean up last line.
	(cygsid_getfromgr): Ditto.
	(is_grp_member): Use getpwuid32 and getgrgid32.
	* uinfo.cc (internal_getlogin): Set DEFAULT_GID at start.
	Use getpwsid. Move the read of /etc/group after the second access
	to /etc/passwd.  Change some debug_printf.