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/unix/Makefile.src

@@ -354,9 +354,9 @@ CSOURCES = $(HACKCSRC) $(SYSSRC) $(WINCSRC) $(GENCSRC)
 # and dgn_comp.h, dgn_file.h, lev_comp.h, special level & dungeon files.
 #
 HACKINCL = align.h amiconf.h artifact.h artilist.h attrib.h beconf.h color.h \
-	config.h config1.h coord.h decl.h def_os2.h display.h dlb.h dungeon.h \
-	edog.h emin.h engrave.h epri.h eshk.h extern.h flag.h func_tab.h \
-	global.h hack.h lev.h macconf.h mfndpos.h micro.h mkroom.h \
+	config.h config1.h context.h coord.h decl.h def_os2.h display.h dlb.h \
+	dungeon.h edog.h emin.h engrave.h epri.h eshk.h extern.h flag.h \ 
+	func_tab.h global.h hack.h lev.h macconf.h mfndpos.h micro.h mkroom.h \
 	monattk.h mondata.h monflag.h monst.h monsym.h obj.h objclass.h \
 	os2conf.h patchlevel.h pcconf.h permonst.h prop.h rect.h region.h rm.h \
 	sp_lev.h spell.h system.h tcap.h timeout.h tosconf.h tradstdc.h \