patch 8.1.0036: not restoring Insert mode if leaving prompt buffer with mouse

Problem:    Not restoring Insert mode if leaving a prompt buffer by using a
            mouse click.
Solution:   Set b_prompt_insert appropriately. Also correct cursor position
            when moving cursor to last line.

src/buffer.c

@@ -5733,6 +5733,10 @@ buf_spname(buf_T *buf)
 #endif
 	if (buf->b_fname != NULL)
 	    return buf->b_fname;
+#ifdef FEAT_JOB_CHANNEL
+	if (bt_prompt(buf))
+	    return (char_u *)_("[Prompt]");
+#endif
 	return (char_u *)_("[Scratch]");
     }