trunk only: preserving context (sys 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

sys/os2/Makefile.os2

@@ -714,7 +714,7 @@ YOU_H	   = $(INCL)\you.h $(INCL)\attrib.h $(PERMONST_H) $(INCL)\mondata.h \
 	     $(INCL)\monst.h $(INCL)\youprop.h $(INCL)\prop.h $(INCL)\pm.h
 DECL_H	   = $(INCL)\decl.h $(INCL)\spell.h $(INCL)\obj.h $(YOU_H) \
 	     $(INCL)\onames.h $(INCL)\color.h
-HACK_H	   = $(CONFIG_H) $(DECL_H) $(INCL)\monsym.h $(INCL)\mkroom.h \
+HACK_H	   = $(CONFIG_H) $(INCL)\context.h $(DECL_H) $(INCL)\monsym.h $(INCL)\mkroom.h \
 	     $(INCL)\objclass.h $(TRAP_H) $(INCL)\engrave.h $(INCL)\flag.h \
 	     $(INCL)\rm.h $(INCL)\dungeon.h $(INCL)\hack.h $(INCL)\display.h \
 	     $(INCL)\vision.h $(INCL)\wintty.h $(INCL)\wintype.h $(INCL)\align.h \