patch 8.0.0899: function name mch_stop_job() is confusing

Problem:    Function name mch_stop_job() is confusing.
Solution:   Rename to mch_signal_job().
diff --git a/src/os_win32.c b/src/os_win32.c
index 2ee3f2e..9dc039b 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -5248,7 +5248,7 @@
  * Return FAIL if it didn't work.
  */
     int
-mch_stop_job(job_T *job, char_u *how)
+mch_signal_job(job_T *job, char_u *how)
 {
     int ret;