patch 8.1.0953: a very long file is truncated at 2^31 lines

Problem:    A very long file is truncated at 2^31 lines.
Solution:   Use LONG_MAX for MAXLNUM. (Dominique Pelle, closes #4011)
diff --git a/src/version.c b/src/version.c
index 16ab493..a266ce0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    953,
+/**/
     952,
 /**/
     951,