patch 9.0.1336: functions without arguments are not always declared properly

Problem:    Functions without arguments are not always declared properly.
Solution:   Use "(void)" instead of "()". (Yegappan Lakshmanan, closes #12031)
diff --git a/src/job.c b/src/job.c
index ddfc8ef..c3ba3b8 100644
--- a/src/job.c
+++ b/src/job.c
@@ -885,7 +885,7 @@
  * Return TRUE when there is any running job that we care about.
  */
     int
-job_any_running()
+job_any_running(void)
 {
     job_T	*job;
 
@@ -1655,7 +1655,7 @@
  * Return TRUE if the cursor is in the editable position of the prompt line.
  */
     int
-prompt_curpos_editable()
+prompt_curpos_editable(void)
 {
     return curwin->w_cursor.lnum == curbuf->b_ml.ml_line_count
 	&& curwin->w_cursor.col >= (int)STRLEN(prompt_text());