Allow passing additional parameters to shell_exec()

This allows for specifying multiple command line parameters to be passed
on to the command in a way similar to fork_exec(). This is useful if we
want to wrap editor or pager invocations in a shell.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/todo.c

@@ -469,6 +469,7 @@ void
 todo_pipe_item (void)
 {
   char cmd[BUFSIZ] = "";
+  char const *arg[] = { cmd, NULL };
   int pout;
   int pid;
   FILE *fpout;
@@ -479,7 +480,7 @@ todo_pipe_item (void)
     return;
 
   wins_prepare_external ();
-  if ((pid = shell_exec (NULL, &pout, cmd)))
+  if ((pid = shell_exec (NULL, &pout, *arg, arg)))
     {
       fpout = fdopen (pout, "w");