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/botl.c

@@ -286,7 +286,7 @@ bot()
 {
 	bot1();
 	bot2();
-	flags.botl = flags.botlx = 0;
+	context.botl = context.botlx = 0;
 }
 
 /*botl.c*/