Ticket #213 [mc-ru-fork] patch for fix bug 'The shell is already running a command'

Test case:

- run mc
- press CTRL+o (hide panels)
- press 'space' key
- press 'backspace' key
- press CTRL+o (show panels)
- type 'ls' and press 'enter' key

Fix issue: Now 'busy shell' status toggle on if user will press 'Enter' key.
Old behavior: User was press any key into subshell and 'busy shell' status toggle on.

Also, patch will enter new behavior:
 * run mc
 * press ctrl+o (hide panels)
 * type 'cat ' and don't press 'Enter' key
 * press ctrl+o (show panels)
 * type 'ls' and press enter

You'll see:
cat: ls: File not found.

Signed-off-by: Slava Zanko <slavazanko@gmail.com>

src/subshell.c

@@ -573,6 +573,7 @@ int invoke_subshell (const char *command, int how, char **new_dir)
 	    subshell_state = ACTIVE;
 	    /* FIXME: possibly take out this hack; the user can
 	       re-play it by hitting C-hyphen a few times! */
+	    if (subshell_ready)
 		write_all (subshell_pty, " \b", 2);  /* Hack to make prompt reappear */
 	}
     }
@@ -1052,6 +1053,8 @@ feed_subshell (int how, int fail_on_error)
 		}
 
 	    write_all (subshell_pty, pty_buffer, bytes);
+
+	    if (pty_buffer[bytes-1] == '\n' || pty_buffer[bytes-1] == '\r')
 		subshell_ready = FALSE;
 	} else {
 	    return FALSE;