win32.h: declare fstati64 to suppress warnings

* include/ruby/win32.h (fstati64): declare for ext/-test-/file/stat.c
  on w64-mingw, to suppress warnings.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43281 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

include/ruby/win32.h

@@ -459,6 +459,8 @@ extern rb_gid_t  getegid (void);
 extern int       setuid (rb_uid_t);
 extern int       setgid (rb_gid_t);
 
+extern int fstati64(int, struct stati64 *);
+
 extern char *rb_w32_strerror(int);
 
 #ifdef RUBY_EXPORT