Some more changes from Michael K. Johnson for Linux.

Some more changes from Michael K. Johnson for Linux.
	* s/template.h: Mention that you should #define HAVE_TERMIO or
	HAVE_TERMIOS, but not both, and that HAVE_TERMIOS is preferred.
	* systty.h (EMACS_SET_TTY_PGRP): Don't assign the return value of
	tcsetpgrp to *pgid; it's just a status value.
	* config.h.in (HAVE_RANDOM): This shouldn't be defined on Linux
	systems using XFree386, and perhaps is inappropriate in general.
	* m/intel386.h: #undefine the integer size macros, since the Linux
	<values.h> file #defines them itself.
	* mem-limits.h (get_lim_data): Linux has the ulimit call; if it
	fails, fall back on ULIMIT_BREAK_VALUE.
	* process.c: Linux needs the WAITTYPE, etc. definitions.
	* unexec.c (hdr, ohdr): Linux has the ordinary `struct exec' type;
	no need to use SYSV names.
	* s/linux.h: New file.