patch 8.0.1703: in the tutor 'showcmd' is not set

Problem:    In the tutor 'showcmd' is not set.
Solution:   Set 'showcmd' in the vimtutor script. (Ken Takata, closes #2792)
diff --git a/src/vimtutor b/src/vimtutor
index e53201d..1e8769b 100755
--- a/src/vimtutor
+++ b/src/vimtutor
@@ -70,5 +70,5 @@
 # The script tutor.vim tells Vim which file to copy
 $VIM -f -u NONE -c 'so $VIMRUNTIME/tutor/tutor.vim'
 
-# Start vim without any .vimrc, set 'nocompatible'
-$VIM -f -u NONE -c "set nocp" $TUTORCOPY
+# Start vim without any .vimrc, set 'nocompatible' and 'showcmd'
+$VIM -f -u NONE -c "set nocp showcmd" $TUTORCOPY