patch 7.4.1976
Problem:    Number variables are not 64 bits while they could be.
Solution:   Add the num64 feature. (Ken Takata)
diff --git a/src/charset.c b/src/charset.c
index e008399..9fcd88c 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1836,14 +1836,14 @@
 				       is bin */
     int			*len,	    /* return: detected length of number */
     int			what,	    /* what numbers to recognize */
-    long		*nptr,	    /* return: signed result */
-    unsigned long	*unptr,	    /* return: unsigned result */
+    varnumber_T		*nptr,	    /* return: signed result */
+    uvarnumber_T	*unptr,	    /* return: unsigned result */
     int			maxlen)     /* max length of string to check */
 {
     char_u	    *ptr = start;
     int		    pre = 0;		/* default is decimal */
     int		    negative = FALSE;
-    unsigned long   un = 0;
+    uvarnumber_T    un = 0;
     int		    n;
 
     if (ptr[0] == '-')
@@ -1912,7 +1912,7 @@
 	/* octal */
 	while ('0' <= *ptr && *ptr <= '7')
 	{
-	    un = 8 * un + (unsigned long)(*ptr - '0');
+	    un = 8 * un + (uvarnumber_T)(*ptr - '0');
 	    ++ptr;
 	    if (n++ == maxlen)
 		break;
@@ -1925,7 +1925,7 @@
 	    n += 2;	    /* skip over "0x" */
 	while (vim_isxdigit(*ptr))
 	{
-	    un = 16 * un + (unsigned long)hex2nr(*ptr);
+	    un = 16 * un + (uvarnumber_T)hex2nr(*ptr);
 	    ++ptr;
 	    if (n++ == maxlen)
 		break;
@@ -1936,7 +1936,7 @@
 	/* decimal */
 	while (VIM_ISDIGIT(*ptr))
 	{
-	    un = 10 * un + (unsigned long)(*ptr - '0');
+	    un = 10 * un + (uvarnumber_T)(*ptr - '0');
 	    ++ptr;
 	    if (n++ == maxlen)
 		break;
@@ -1950,9 +1950,9 @@
     if (nptr != NULL)
     {
 	if (negative)   /* account for leading '-' for decimal numbers */
-	    *nptr = -(long)un;
+	    *nptr = -(varnumber_T)un;
 	else
-	    *nptr = (long)un;
+	    *nptr = (varnumber_T)un;
     }
     if (unptr != NULL)
 	*unptr = un;