Fix window resize bug after exiting to ksh from vim (re: f1c8ecc) (#865)

Reproducer (for a terminal with fullscreen support):
$ <F11>          # Maximize terminal to occupy entire screen
$ vim            # Open vim editor
: <F11>          # Unmaximize while in vim
: q!             # Quit vim
$ /b<Tab><Tab>   # Attempt to obtain completion list; triggers bug
$ kill -WINCH $$
$ /b<Tab><Tab>   # List works again after SIGWINCH

edit.c:
- Readd removed calls to sh_winsize() to fix the regression
  in the tab completion menu. The purpose of these is to
  obtain the correct window size in cases where ksh does
  not get sent SIGWINCH after the window size changes.
  Perhaps this is 'inefficient', but correct behavior
  is better (assuming such efficiency even matters that
  much in the editor modes).

Author: JohnoKing

src/cmd/ksh93/edit/edit.c

@@ -246,7 +246,9 @@ int tty_raw(int fd, int echomode)
  */
 int ed_window(void)
 {
-	int	cols = sh.columns - 1;
+	int	cols;
+	sh_winsize();
+	cols = sh.columns - 1;
 	if(cols < MINWINDOW)
 		cols = MINWINDOW;
 	else if(cols > MAXWINDOW)
@@ -624,6 +626,7 @@ int ed_read(void *context, int fd, char *buff, int size, int reedit)
 				flush_notifybuf();
 				goto skipwinch;
 			}
+			sh_winsize();
 			ed_putchar(ep,'\r');
 			/*
 			 * Try to move cursor to start of first line and pray it works... it's very