patch 8.2.2675: directory change in a terminal window shell is not followed

Problem:    Directory change in a terminal window shell is not followed.
Solution:   Add the 'autoshelldir' option. (closes #6290)
diff --git a/src/option.h b/src/option.h
index 349268c..0b1183f 100644
--- a/src/option.h
+++ b/src/option.h
@@ -383,6 +383,9 @@
 #ifdef FEAT_AUTOCHDIR
 EXTERN int	p_acd;		// 'autochdir'
 #endif
+#ifdef FEAT_AUTOSHELLDIR
+EXTERN int	p_asd;		// 'autoshelldir'
+#endif
 EXTERN int	p_ai;		// 'autoindent'
 EXTERN int	p_bin;		// 'binary'
 EXTERN int	p_bomb;		// 'bomb'