patch 8.0.0503: endless loop in updating folds with 32 bit ints

Problem:    Endless loop in updating folds with 32 bit ints.
Solution:   Subtract from LHS instead of add to the RHS. (Matthew Malcomson)

Author: brammool

src/fold.c

@@ -2755,7 +2755,7 @@ foldUpdateIEMSRecurse(
 	/* End of fold found, update the length when it got shorter. */
 	if (fp->fd_len != flp->lnum - fp->fd_top)
 	{
-	    if (fp->fd_top + fp->fd_len > bot + 1)
+	    if (fp->fd_top + fp->fd_len - 1 > bot)
 	    {
 		/* fold continued below bot */
 		if (getlevel == foldlevelMarker

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    503,
 /**/
     502,
 /**/