eliminate static analysis complaints about eat.c

This is fairly ridiculous but it prevents the bogus complaints
when compiling eat.c with 'gcc -fanalyzer' about some fields in
gc.context.victual being used without having been initialized.

There's bound to be a better way to handle this and I'm curious
whether it will work with the 'onefile' testing.

include/extern.h

@@ -332,6 +332,7 @@ extern void destroy_drawbridge(coordxy, coordxy);
 /* ### decl.c ### */
 
 extern void decl_globals_init(void);
+extern void sa_victual(volatile struct victual_info *);
 
 /* ### detect.c ### */