trunk only: preserving context (src files)

Pat Rankin wrote:
> collect them all into some new struct and
> save that separately rather than jamming more non-option stuff
> into struct flags.

This patch:
- collects all context/tracking related fields from flags
  into a new structure called "context."
It also adds the following to the new structure:
- stethoscope turn support
- victual support
- tin support

src/engrave.c

@@ -331,7 +331,7 @@ register int x,y;
 			et = ep->engr_txt;
 		You("%s: \"%s\".",
 		      (Blind) ? "feel the words" : "read",  et);
-		if(flags.run > 1) nomul(0);
+		if(context.run > 1) nomul(0);
 	    }
 	}
 }