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/priest.c

@@ -447,7 +447,7 @@ register struct monst *priest;
 		    else
 			u.ugold = 1L;
 		    priest->mgold -= u.ugold;
-		    flags.botl = 1;
+		    context.botl = 1;
 #else
 	if(!money_cnt(invent)) {
 	    if(coaligned && !strayed) {