Handle the escape sequence for the End key (#75)

Many terminals (xterm being one example) give the Home and End keys
the escape sequences '^[[H' and '^[[F'. The first sequence is
handled in both editing modes by moving the cursor to start of
line, but ksh ignored the second sequence.

src/cmd/ksh93/edit/emacs.c,
src/cmd/ksh93/edit/vi.c:
- Add case labels for '^[[F' so that in both editing modes the End
  key moves the cursor to the end of the line.

NEWS

@@ -10,6 +10,10 @@ Any uppercase BUG_* names are modernish shell bug IDs.
   that 'unalias -a' does not remove them. Shell functions can now use
   these names, which improves compatibility with POSIX shell scripts.
 
+- The End key escape sequence '^[[F' is now handled in the emacs and vi editing
+  modes. The End key moves the cursor to the end of the line (in contrast to
+  the Home key doing the opposite).
+
 2020-07-14:
 
 - Fixed a bug that caused 'set -b' to have no effect.

src/cmd/ksh93/edit/emacs.c

@@ -1105,6 +1105,7 @@ static int escape(register Emacs_t* ep,register genchar *out,int count)
 			    case 'H':
 				ed_ungetchar(ep->ed,cntl('A'));
 				return(-1);
+			    case 'F':
 			    case 'Y':
 				ed_ungetchar(ep->ed,cntl('E'));
 				return(-1);

src/cmd/ksh93/edit/vi.c

@@ -1669,6 +1669,7 @@ static int mvcursor(register Vi_t* vp,register int motion)
 		    case 'H':
 			tcur_virt = 0;
 			break;
+		    case 'F':
 		    case 'Y':
 			tcur_virt = last_virt;
 			break;