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/mon.c

@@ -283,7 +283,7 @@ register struct monst *mtmp;
 
 	/* if polymorph or undead turning has killed this monster,
 	   prevent the same attack beam from hitting its corpse */
-	if (flags.bypasses) bypass_obj(obj);
+	if (context.bypasses) bypass_obj(obj);
 
 	if (mtmp->mnamelth)
 	    obj = oname(obj, NAME(mtmp));
@@ -484,7 +484,7 @@ struct monst *mon;
 
 #ifdef STEED
     if (mon == u.usteed) {
-	if (u.ugallop && flags.mv) {
+	if (u.ugallop && context.mv) {
 	    /* average movement is 1.50 times normal */
 	    mmove = ((rn2(2) ? 4 : 5) * mmove) / 3;
 	}
@@ -2075,7 +2075,7 @@ register struct monst *mtmp;
 	}
 
 	/* attacking your own quest leader will anger his or her guardians */
-	if (!flags.mon_moving &&	/* should always be the case here */
+	if (!context.mon_moving &&	/* should always be the case here */
 		mtmp->data == &mons[quest_info(MS_LEADER)]) {
 	    struct monst *mon;
 	    struct permonst *q_guardian = &mons[quest_info(MS_GUARDIAN)];
@@ -2103,7 +2103,7 @@ register struct monst *mtmp;
 	mtmp->meating = 0;	/* assume there's no salvagable food left */
 	setmangry(mtmp);
 	if(mtmp->m_ap_type) seemimic(mtmp);
-	else if (flags.forcefight && !flags.mon_moving && mtmp->mundetected) {
+	else if (context.forcefight && !context.mon_moving && mtmp->mundetected) {
 	    mtmp->mundetected = 0;
 	    newsym(mtmp->mx, mtmp->my);
 	}
@@ -2498,7 +2498,7 @@ boolean msg;		/* "The oldmon turns into a newmon!" */
 	mon_break_armor(mtmp, polyspot);
 	if (!(mtmp->misc_worn_check & W_ARMG))
 	    mselftouch(mtmp, "No longer petrify-resistant, ",
-			!flags.mon_moving);
+			!context.mon_moving);
 	m_dowear(mtmp, FALSE);
 
 	/* This ought to re-test can_carry() on each item in the inventory