trunk only: preserving context (remaining 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

win/win32/tilemap.dsp

@@ -126,6 +126,10 @@ SOURCE=..\include\config1.h
 # End Source File
 # Begin Source File
 
+SOURCE=..\include\context.h
+# End Source File
+# Begin Source File
+
 SOURCE=..\include\coord.h
 # End Source File
 # Begin Source File