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.

Author: brammool

src/spellfile.c

@@ -1585,7 +1585,7 @@ spell_read_tree(
     int		prefixtree,	/* TRUE for the prefix tree */
     int		prefixcnt)	/* when "prefixtree" is TRUE: prefix count */
 {
-    int		len;
+    long	len;
     int		idx;
     char_u	*bp;
     idx_T	*ip;
@@ -1595,7 +1595,7 @@ spell_read_tree(
     len = get4c(fd);
     if (len < 0)
 	return SP_TRUNCERROR;
-    if (len >= 0x3ffffff)
+    if (len >= LONG_MAX / (long)sizeof(int))
 	/* Invalid length, multiply with sizeof(int) would overflow. */
 	return SP_FORMERROR;
     if (len > 0)

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    376,
 /**/
     375,
 /**/