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/proto/os_unix.pro b/src/proto/os_unix.pro
index 8e955aa..20765c0 100644
--- a/src/proto/os_unix.pro
+++ b/src/proto/os_unix.pro
@@ -63,7 +63,7 @@
 void mch_job_start(char **argv, job_T *job, jobopt_T *options);
 char *mch_job_status(job_T *job);
 job_T *mch_detect_ended_job(job_T *job_list);
-int mch_stop_job(job_T *job, char_u *how);
+int mch_signal_job(job_T *job, char_u *how);
 void mch_clear_job(job_T *job);
 void mch_breakcheck(int force);
 int mch_expandpath(garray_T *gap, char_u *path, int flags);