* startup.el: Streamline code in several functions and use a more

* startup.el: Streamline code in several functions and use a more
	consistent idiom within the file, for ease of reading and
	maintenance.  Rephrase booleans to avoid `(not noninteractive)'.
	Clarify several booleans expressions using De Morgan's laws.

	(command-line): Fix barf when first command-line option handled by
	`command-line-1' is in the form --OPT=VAL.
	(command-line-1): Restore intended behavior of the --directory/-L
	command-line option: "-L a -L b -L c" on the command-line now puts
	'(a b c) at the front of `load-path'.