feature request- command line define flags ( like apache -D )

[Jonathan Vanasco]

Apache lets one do this:

	apachectl start -D VariableName

and in the config

	<ifDefine VariableName>
		Do Stuff if we specified the variable
	</ifDefine>
	<ifDefine !VariableName>
		or Don't Do Stuff if we didn't specify it
	</ifDefine>

nginx doesn't seem to have that facility (at least in the docs it  
doesnt).  I was hoping it could be added if its not in there already

why is it useful?
	i use it on apache to switch from uptime -> downtime when there's  
only 1-2 lines different in the config files.  big timesaver.
	also, when you're hosting mutiple sites,  you might want to include  
a different file depending on a flag being set or not