ldgram.y tidies

I've been tripped up before thinking the "end" rule was the "END"
token.  Let's use a better name.  The formatting changes are for
consistency within rules, and making it a little easier to visually
separate tokens from mid-rule actions.

	* ldgram.y (separator): Rename from "end".  Update uses.
	(statement): Formatting.  Move ';' match to beginning.
	(paren_script_name): Formatting.  Simplify.
	(must_be_exp, section): Formatting.