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/timeout.c

@@ -146,7 +146,7 @@ burn_away_slime()
 	if (Slimed) {
 	    pline_The("slime that covers you is burned away!");
 	    Slimed = 0L;
-	    flags.botl = 1;
+	    context.botl = 1;
 	}
 	return;
 }