Fix the Alt+D and Alt+H keyboard shortcuts in emacs mode (#178)

This commit fixes the functionality of Alt+D and Alt+H in emacs mode.
These keyboard shortcuts are intended to work on whole words, but
after commit 13c3fb21 their functionality was reduced to deleting only
singular letters:

$ Test word <Alt+H>    # This should delete 'word', not just 'd'.
$ Foo <Alt+B> <Alt+D>  # This should delete 'Foo', not just 'F'.

Man page entries for reference:
  M-d       Delete current word.
  M-^H      (Meta-backspace) Delete previous word.
  M-h       Delete previous word.

src/cmd/ksh93/edit/emacs.c:
- 'count' cannot be overridden when handling Alt+D or Alt+H,
  so add the total number of repetitions to count (the number of
  repetitions can't be negative).
- If 'count' is a negative number, set it to one before adding the
  number of repetitions.

NEWS

@@ -5,6 +5,9 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 
 2021-02-15:
 
+- Fixed a bug in the emacs built-in editor, introduced on 2020-09-17, that
+  made the Meta-D and Meta-H keys delete single characters instead of words.
+
 - A new 'backslashctrl' shell option has been added. It is on by default.
   Turning it off (set +o backslashctrl or set --nobackslashctrl) disables the
   special escaping behaviour of the backslash character in the emacs and vi

src/cmd/ksh93/edit/emacs.c

@@ -318,13 +318,13 @@ int ed_emacsread(void *context, int fd,char *buff,int scend, int reedit)
 			killing = 0;
 #endif
 		oadjust = count = adjust;
-		if(vt220_save_repeat)
-		{
-			count = vt220_save_repeat;
-			vt220_save_repeat = 0;
-		}
 		if(count<0)
 			count = 1;
+		if(vt220_save_repeat>0)
+		{
+			count += vt220_save_repeat;
+			vt220_save_repeat = 0;
+		}
 		adjust = -1;
 		i = cur;
 		if(c!='\t' && c!=ESC && !digit(c))