patch 8.0.0376: size computations in spell file reading are off

Problem:    Size computations in spell file reading are not exactly right.
Solution:   Make "len" a "long" and check with LONG_MAX.
diff --git a/src/version.c b/src/version.c
index 58ece75..8d14541 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    376,
+/**/
     375,
 /**/
     374,