patch 8.2.0019: cannot number of lines of another buffer

Problem:    Cannot number of lines of another buffer.
Solution:   Add "linecount" to getbufinfo(). (Yasuhiro Matsumoto,
            closes #5370)
diff --git a/src/evalbuffer.c b/src/evalbuffer.c
index a475165..09db525 100644
--- a/src/evalbuffer.c
+++ b/src/evalbuffer.c
@@ -545,6 +545,7 @@
     dict_add_string(dict, "name", buf->b_ffname);
     dict_add_number(dict, "lnum", buf == curbuf ? curwin->w_cursor.lnum
 						     : buflist_findlnum(buf));
+    dict_add_number(dict, "linecount", buf->b_ml.ml_line_count);
     dict_add_number(dict, "loaded", buf->b_ml.ml_mfp != NULL);
     dict_add_number(dict, "listed", buf->b_p_bl);
     dict_add_number(dict, "changed", bufIsChanged(buf));