gas_init

Rename gas_late_init to plain gas_init, to reinforce the idea that
this is where the bulk of gas initialisation belongs.  Also reorder
some initialisation.

	* as.c (gas_init): Rename from gas_late_init.  Open output
	file and arrange for dump_statistics to be called here rather
	than in main.  Create .gasversion. local symbol earlier,
	because we can.